Probably was too scared to endorse him pre-election due to fear of getting cancelled, considering he still has one foot in Hollywood.

I heard that after the election, a lot of Hollywood actors and other entertainers reached out to Joe Rogan thanking him for his bravery and said that they also supported Trump, but were too scared to voice it publicly before the election results came out.

Denzel Washington is another celeb that I suspect also secretly supports Trump but prefers to stay politically neutral in public as to not alienate half his audience.