How should we explain Yaʿaqov’s apparent skepticism toward Yeshua and his later prominence in the Jerusalem Jesus movement?

John 7:5 states that Yeshua’s brothers did not believe in him during his ministry. Yet Paul later identifies Yaʿaqov as “the Lord’s brother” (Gal. 1:19), names him alongside Cephas and John as one of the “pillars” (Gal. 2:9), and preserves an early tradition that the risen Yeshua appeared specifically to him (1 Cor. 15:7).

Within the context of late Second Temple Judaism, how should this apparent shift be understood? Is it plausible that Yaʿaqov initially found his brother’s mission difficult to reconcile with the diverse Jewish expectations surrounding the Mashiach, especially given Yeshua’s eschatological proclamation of the coming Malkhut Shamayim and his participation in contemporary halakhic disputes over Torah?

More importantly, how much historical weight can be placed on the appearance tradition in 1 Corinthians 15:7? Is there any basis for connecting it with Yaʿaqov’s subsequent emergence as a leading figure in the Jerusalem community, or would that go beyond what our earliest sources actually allow us to reconstruct?