Edit: Well, I guess these tweets explain the beef well -
https://twitter.com/elonmusk/status/1606642155346612229
https://twitter.com/elonmusk/status/1626516035863212034
Not what I intended at all." - Elon
You can think what you want of Elon, but he is in the right here.
Maybe they just wants to express how much they don't like Elon any opportunity they gets.
I would add this one:
https://twitter.com/elonmusk/status/1630640058507116553
I had no idea about this drama either, so I didn't understand what Elon was talking about, now it seems clear.
But "Based"? Is it the name of his new AI company? Where does that come from?
See also "pilled."
It is also a catchphrase of the extremely online left with exactly the same in-group vs. out-group implication (and, amusingly—because of the different meanings of “liberal” and “lib” favored by the two sides—usually identical meaning with regard to “libs/normies”.)