You mean advertisers who would be willing to target consumers who dislike how the incredibly rich have disproportionately large control of the economy?

You also have advertisers willing to target the outrage crowd, so they would also stand to gain from the post.

Not all advertisers care about the things that advertisers from companies like Disney or the NFL care about.

The current wave of it started with Old Spice TV commercials and Dennys Tumblr.

From there it has spread to numerous other brands like Moon Pies, Sunny Delight, etc. Many snack and food brands were highly visible early adopters of this iteration of internet culture as a way to rep their brands.

There's a huge difference between mean-spirited user-generated shitposts and quirky advertising campaign. You're talking about the latter. Crucially, an advertising campaign is carefully crafted and gets approval, whereas millions of shitposts you might potentially advertise online are not and do not, and many of them pose a brand risk to be associated with.

So I ask again, show me examples of advertisers that enthusiastically advertise on shitposts.

Sure, and no true scotsman puts sugar on his porridge.

Your own chosen example was Elon Musk recent twitter history. Debating the difference between your chosen example and Dennys to identify an obvious principle that distinguishes them is asking people to play calvinball with you.