Have you got any evidence that "Buddha's writing were compiled at conference shortly after his death"?
People can't even agree on when he lived after all, and it's generally assumed it was an oral tradition for centuries before the first writings.
You appear to agree concerning the problem of the historicity of the life of Buddha..
The Historicity of the first or possibly the second Council is generally accepted even though we do not have the actual writings presented. The historicity of some of participants at the First Council is accepted. As with the history and dating of the scripture of Christianity the history is not resolved. There are as many clouds over the history Christian scripture as with the origins of Buddhist scripture. That is the main point of my argument is in other religions have similar problems of historicity as Christianity. Actuall the Pentateuch of Judaism has more problems of provenance and authorship than Christianity, Taoism or Buddhism,
From:
First Buddhist council - Wikipedia
Historicity
Tradition states that the First Council lasts for seven months.
[9] Scholars doubt, however, whether the entire canon was really recited during the First Council,
[1] because the early texts contain different accounts on important subjects such as meditation.
[10] It may be, though, that early versions were recited of what is now known as the
Vinaya-piṭaka and
Sutta-piṭaka.
[11] Nevertheless, many scholars, from the late 19th century onward, have considered the historicity of the First Council improbable. Some scholars, such as orientalists
Louis de La Vallée-Poussin and D.P. Minayeff, thought there must have been assemblies after the Buddha's death, but considered only the main characters and some events before or after the First Council historical.
[12][13] Other scholars, such as Buddhologist
André Bareau and Indologist
Hermann Oldenberg, considered it likely that the account of the First Council was written after the
Second Council, and based on that of the second, since there were not any major problems to solve after the
Buddha's death, or any other need to organize the First Council.
[14][15] On the other hand, archaeologist
Louis Finot, Indologist E. E. Obermiller and to some extent Indologist Nalinaksha Dutt thought the account of the First Council was authentic, because of the correspondences between the Pāli texts and the
Sanskrit traditions.
[16] Indologist
Richard Gombrich, following
Bhikkhu Sujato and Bhikkhu Brahmali's arguments, states that "it makes good sense to believe ... that large parts of the Pali Canon do preserve for us the
Buddha-vacana, 'the Buddha's words', transmitted to us via his disciple Ānanda and the First Council".
[17]"