When I say that Gentiles caused the Jesus Legend (by merely writing the Earliest Gospel euhemerizing the previous Jewish Mythical Jesus), I mean precisely Gnostics on the margin of Judaism, not Gentiles tout court (because otherwise even the Romans of Titus could euhemerize the mythical Jesus!). I accept fully this description of these Gnostics who became Christians in the early II century CE:
The most likely place to find our quarry is in the penumbra surrounding Judaism, consisting of people on their way in or on their way out. These are basically Gentiles who are attracted by Judaism enough to study it or to seek acquaintance eith knowledgeable Jews. Some pursue their study far enough to become actually converted to Judaism, but find Jewish observance too strenuous or too alien, and lapse. Others only reach the status of 'God-fearers', attend the synagogues in this capacity, but eventually become resentful of the inferior status accorded them. Others never actually declare or renounce allegiance to Judaism, but, having become the targets of Jewish missionary activity, acquire a considerable smattering of Jewish knowledge, and feel constrained to formulate some attitude towards Judaism. Such marginal people develop ambivalent feelings towards Judaism. On the other hand, they feel it to be a force to be reckoned with; on the other hand, they feel a certain resentment at the impudence of this barbarian faith in professing to be superior to the spiritual claims of Hellenistic culture; or, if they have gone so far as to succumb to Judaism for a while, they feel a corresponding need, after lapsing from Judaism, to justify their reversal of attitude and to reassert the superiority of the Hellenism from which they had temporarily defected. The most likely place to find such people in numbers sufficient to give rise to a distinctive religious grouping is Alexandria, where Jewish missionary activity was confident and even sometimes aggressive. The unease at such activity and the need to fight suscettibility to it, or to justify withdrawal from it after initial acceptance, could lead to a religious movement that contrasted the superior spiritual quality of Hellenism with the materiality and this-worldly stance of Judaism, while at the same time Accounting for Judaism and explaining its proper place in the scheme of things.
(Hyam Maccoby, Paul and Hellenism, p. 31-32, SCM Press, London)
Hence it is excluded 100% any possible connection with Egyptian myths at the origin of Christian Gnosis.