Just so we're clear;
Joe Biden courting moderates/Republicans is nonsense.
Bernie Sanders courting Fox News viewers and Joe Rogans likely conservative-leaving audience is savvy politics.
When people criticize moderates for trying to appeal to Republicans, they criticize the idea of compromising your progressive ideas in a bid to appear more palatable to conservatives. In effect, centrist democrats just make the needle of the party move ever further to the right by always conceding things to Republicans. And they hope that Republicans will reciprocate eventually and be a bit more progressive in return, except they never do. They take, but they never give. Here's a good video on the subject (this is a whole series, and it's been a while since I've watched it, so I hope this is the right episode, but the whole series is worth a watch or five, to be honest):
Basically: Conservatives/Republicans tend to play dirty, while liberals/Democrats tend to try and play fair, and so the latter are all about reasoning, dialogue, due process and having the philosophical high ground, but that can never work when the former doesn't care and will never extend an olive branch.
Now, I'm not very familiar with what Biden does specifically in that respect, so I can't speak as to his tactics, but that's not what Sanders has been doing so far. If you listen to his interview on Rogan's podcast, he says pretty much the same things he's been saying all this time, without co-opting any conservative talking points in an attempt to cater to Rogan or Rogan's audience. Even the tweet on Bernie's official account does nothing of the sort.
With that said, back on-topic, the tweet is still shitty. Rogan may be an impressionable dunce, but he still very much harbors racist and transphobic views. Cutting a campaign ad acknowledging his endorsement might not be literally the same thing as saying "Rogan is awesome and Bernie very much likes his views", but it still platforms him and shows some degree of (real or perceived) association with his content. I don't think it will matter much in the long run because the ad and the tweet don't literally support or even thank Rogan, and it's pretty clear that Bernie himself is, by and large, inclusive, but it's still clumsy at best, and it shouldn't surprise anyone that trans people or black people, among others, would be hurt by that move.