I don’t know the exact details of why he left, but I can say that a lot of us were surprised and confused when he joined Remix. The other Remix founders have great reputations everywhere they’ve worked, but Kent has kind of developed into a personality cult over the years.

His courses and personal brand have no doubt been very profitable for him, so I’m not too surprised to see him go back toward personal brand building and trying to increase the reach of his courses.

I have a lot of respect for education initiatives and efforts to create educational content, but I’ve also had to do a lot of “deprogramming” of juniors who consumed a lot of Kent C Dodds material and end up trying to overengineer everything. He also had an expensive React testing course a couple years ago that was really disappointing, which burned a lot of goodwill among the community.

The comments of https://news.ycombinator.com/item?id=28818829 touches on the concerns you've raised.

What are some of the most common practices you've had to "deprogram"? Curious

I noticed some negative reactions whenever Kent would publish content about Remix. I wonder if Kent+other Remix founders felt since reaction to Kent was at times negative, it'd be best for Kent to keep doing his own thing.

My guess is there's way more money in his educational endeavors

That implies he considered Remix a failure and left. Interesting.

I doubt it. Honestly I suspect he saw more money in building content that he owned 100% based on his personal brand, whereas contributing to a project that he only owned a fraction of wasn’t up his alley.

He is a co-founder so I would believe he had more than a fraction of (unvested) stonks. A co-founder that left within a year, and prolly dropped all his shares (cliff, again my assumption).