Reality is not always defined by what is seen (consider science prior to the electron microscope).
Neither can what stirs the heart, metaphorically speaking, be evidenced by a hospital's heart monitor.
When researching religions, one can look at what scholarship has deciphered regarding past events, helping confirm whether something actually occurred or not.
A historian's motivation, identity and ideology can play an influential role regarding their reports or accounts, revealing why a certain fact, opinion or point of view is accepted or denied by them.
Why have Jewish historians agreed with both Roman and Christian historians about the death of Jesus on a cross?
Why would the Jewish religious hierarchy acknowledge Jesus having died if doing so would place them in a losing position?
Jesus claimed to be the Messiah and declared equality with God (quoted having said “before Abraham was, I Am” & “I and the Father are One”).
The Jewish religious hierarchy denied Him these claims and demanded His death.
Why would the Roman political hierarchy acknowledge Jesus having died if doing so would place them in a losing position?
Jesus claimed to be the King of the Jews.
Doing so was asking for the death sentence since a Roman king already reigned as “king of the Jews”: Pontus Pilate.
There isn't a need to mention the Christian historical account since the other two opposing parties (Jewish and Roman) are in agreement regarding Jesus having died on a cross.
If opposing views agree on something having occurred, and no contention arose at the time of the event's occurrence, this may be a good indicator of that event's validity or its truth of having occurred.
Why then does an opinion that Jesus' death not having occurred exist today?
The Muslim community at-large believes (or, is taught) that Jesus did not die on a cross, nor died at all, but instead believes Jesus rose up to heaven without having suffered death.
The event of rising up agrees with the initial Christian account, but not the initial Jewish account... the Roman account also mentioning both sides while not concerned until centuries later.
The idea that death did not occur to Jesus is mentioned in the Quran (a believed-to-be inspired message) and Hadith (reports of what was heard about or from Muhammad).
Muslim and western scholarship shows interpretation and belief regarding Jesus' death being at odds.
Some of the earliest Hadith writings (by “companions of Muhammad”) reported Jesus did die on a cross, with the length of time varying.
What I've found in researching Islam's history, impact, and writings (including the Quran and Hadith and narrative histories), is an array of what can be found in any given culture and ideology:
Fact, fiction, legend, myth and opinion... in other words; man's typical nature being highlighted, some things purposely obscured, other things revised with human fallibility being justified.
Nothing new under the sun.
This is typical of every organized, loosely organized or autonomous group(s) of people throughout time.
Muslim scholarship over the centuries has brought about various concepts and understandings of Jesus... and His proclaimed death and ascension.
Early concepts were first built upon what is mentioned in the Quran and later Hadith, interpreted, and these interpretations further interpreted to follow what has been mentioned in the Quran and Hadith.
The issue of Jesus' death on a cross has grown deeper in contention among the branches of Islam.
As new information is read and discovered, men have come to believe.
Individuals and their groups within Islamic ideology have come to accept the historical fact that Jesus died on a cross.
This is quite amazing, for it is only by faith, as the Gospel message states, that any individual may believe Christ having come in human form, suffered death, and having risen to life!
Faith being a gift from Above, it is not something any individual can muster or develop on their own.
The perception of Jesus within Islamic eschatology (part of theology concerned with death, judgment, and the final destiny of the soul and of humankind) has always been viewed through the lens of the Quran, building from there various ideology through cultural identity (Arabic, Persian, Indian, etc.), further branching out via Hadith, Tafsir (exegesis, or interpretation) and legend.
In recent centuries the Gospel teachings have begun to be considered in defining and understanding who Jesus is in Islam.
The late development is due to a misinterpretation and legendary suspicion that the Gospel message was corrupted, yet scholarship-wise this has yet to be clearly identified.
Where Islam ideology originated, among peoples of the Arabian Peninsula, written record-keeping was nonexistent.
Neighboring Egypt had written records of their historical highlights (religious, mythical and factual) for several millennia prior to Islam.
But sadly, the loose bands of Arabian tribes had no such organization or hierarchy outside of loose associations and mythical / legendary oral traditions of their own.
Having no written record of or for themselves, a population largely uneducated, illiterate and holding to tribal identity and suspicious prejudices would continue their way of life, now finding pride in the thought of a prophet they could call their own.
Written history on its own isn't a factor pointing to facts, as oral tradition doesn't equate to pure legend or fantasy.
From a scholarly approach, if nothing is found in record, it is anyone's guess whose oral tradition is factual, whose story is part legend and whose tale is pure legend.
With a written record, variations could be evidenced and pinpointed as to when something was altered, revised or edited out.
With oral traditions, variances are difficult to identify and the past events difficult to determine.
Islam as a whole is a still developing culture when compared to western civilization(s).
It should then be no surprise that the death of Christ on a cross, being found in Jewish chronicles, Roman accounts and Christian records, was not believed when Muhammad began to warn his listeners about their pagan revelry and tribal disunity.
The scholarship shows the perception of Jesus, from a Muslim's point of view (what a Muslim would be taught by those before them), includes the pre-Islamic writings of heretical 'Christian' groups from the second to fifth centuries.
These heretical accounts are also mentioned in the Quran.
Instead of drawing conclusions from the primary sources of the Gospel, or secondary sources of early Christian writers and historians, or from non-heretical Christian groups, what has been believed of Jesus in Islamic teaching is part fiction and part fact with highly elaborated opinion, despite some legends being in line with Jesus' character, while other legends being quite contrary.
What is seen still among many Muslim ideological adherents is the ancient mannerism of believing folklore, myths and legends... with a resistance, albeit this resistance is slowly loosening now thanks to worldwide communication channels like the internet, to reviewing new and documented information, assisting to form a clearer and believable (God-willing) view of Jesus Christ, His impact the world over, first with western civilizations and now into eastern realms.
The facts are being more difficult to argue away as suspicions, and the myths are slowly being shown for the varying conjecture they've been developed into.
[all claims made herein have their references and citations, and can be shared upon request]