I assumed they were friends as there are several videos of them conversing. The parent comment pointed out that Sean agree's with the negatives about Jon, which could not mean much, but the fact that Jon's negative as described in the Dreknek are really bad indicates to me that Sean likely doesn't view Jon as a good friend anymore. This is surprising to me because I really did enjoy one of their videos where they try and solve a problem together.
The fact that Sean agrees with this critical take of Jon is further evidence of how much Jon has changed since the pandemic.
STB Is the intial's for Sean T Barrett, who also created a software library with the same name.
Seriously, this is why he did it. His ego and arrogance is off the charts and if it wasn't made by him, he thinks it sucks (e.g. he doesn't like Linux, probably because he realizes Torvalds is actually smarter than him). He also doesn't like C++ or Rust, again, it's probably a good indicator he has a deep inferiority complex and so he has to prove he's the smartest person in the world by writing his own, "better" language.
I.e. I don't think he's making a programming language for some "love of creating", I think he's doing it because he has a deep psychological issue/insecurity, which drives his need to always be the "smartest person in the room", his arrogance, the way he dismisses others who don't agree with his viewpoints etc.
Even if you don't like Jon, calling Jai an exercise in arrogance is simply untrue. When he started making Jai in ~2014, there were very few viable alternatives to C/C++ in the systems programming space that offered the kind of expressive power becoming of a langauge built this century. Rust is great, but it prioritising correctness is not always the right choice, especially not for games. Jai introduced many ideas that languages like Zig and Odin ended up adopting.