In my experience, big corporate employers get extremely nervous when their employees start doing anything high profile (i.e. successful) in the political sphere.

After all, if 250 people report to me, probably some of them are going to have opinion A and some are going to have opinion B. If I take a strong public stance in support of A and against B, some of the more nervous B supporters are going to worry I hate them personally and fear I'm a threat to their career - and they're probably going to go to HR about it.

And even if my job doesn't give me any hiring-and-firing powers - if I'm high profile enough that a load of random haters decide they're going to try to get me fired by subjecting my employer to a campaign of harassment, well, now folks like HR and customer services are getting harassed.

Obviously, though, I've never seen a corporation have a blanket policy saying employees can't engage with the political system - that would be pretty bad as a policy. Instead they'll quote policies about 'bringing the company into disrepute' and similar.

It's simpler than that. In his timeline he's showing how he's getting headlines for releasing videos critical of Amazon, his own employer. He was using his position at Amazon to lend more credibility to his platform.