A cult is defined by veneration and devotion dedicated to one individual (or idol) above all else. It typically involves the treatment of that idol as infallible. I fail to understand how Obama appearing on Jimmy Kimmel is even tangentially related to the issue of cult behavior in American politics.
For what it's worth, I'm sure there are Democrats somewhere out there who genuinely do see Obama as an infallible deity. But they are not nearly as organized or numerous as the QAnon movement, and so they do not qualify as a cult. Basic English definitions continue to elude you!
Obama was the premiere "celebrity politician" in the mid 2000s. The fawning over him at the time was something I found rather distasteful, and it was only reinforced by the endless positive media coverage.