He didn't name Musk during the campaign. He presumably thought that'd hurt his chances.

Musk campaigned for him pretty actively. I remember a "chance to win a million dollars if you vote" thing Musk ran in Pennsylvania that was controversial. I don't remember if Musk was part of the official campaign team though, probably not. There were a lot of outsiders, many from the tech scene, in his campaign though. Very obvious show of support from tech billionaires pre-election.