It's a bit of self referencial humor. Like 15 years ago zuck did a live stream or something. On that Livestream he kept awkwardly talking about how much he loves sweet baby Ray's bbq sauce.

I think he did that because knows how detached he comes off as. He was a weirdo before he became a billionaire, and being a part of a separated class of society only made that worse. He also knows how everyone on earth thinks that he's a distrustful person. Plus he's just clearly not comfortable being on camera.

It was basically a failed attempt to come off as relatable and down to earth by sharing something that he has a passion for. Which apparently is grilling. I get it, I like grilling too. But I won't ever be tasked with trying to use that one interest I have as my entire public personality.

He tried something like that before. The reason he wears plain looking tshirts and pants is because it makes him come off as "like one of us" and that he remembers that he came from nothing like the rest of us. But then a few years ago it came out that the black Tshirts he wears costs like $400 each and so does the rest of his outfit.