If the tweets get deleted: that post was made by a different person than the one who resigned, but it seems the latter's resignation was prompted by it.
I can't find the direct link either, but the blog post is quoted as the reason for leaving the Rust project.
Neither happens in a vacuum. There was likely a lot of internet and real-life drama between people. The basis for the blog post already shows some sign of preexisting drama.
I don't know the context so I can only theorize why they quit.
Perhaps they noticed the drama beforehand and this was the final straw. Perhaps they felt called out by the blog post. Perhaps they saw more internet drama coming and decided they've had enough.
Maybe of note: JT has been very influential in a new language originating from the SerenityOS project, Jakt [1], though his contributions died off over time. Perhaps they're searching for a new challenge and saw this as a good moment to get out?
Tl;dr they got invited to talk, the organizers didn't look to closely at the talk, and the talk was rejected or downgraded at the last minute. There is some speculation this was deliberate but I did not see it substantiated. Might have just missed it, though.
Is the blog author the same person as the tweeter? My impression is phantomderp on twitter is the blogger, but the quote tweet is another account.
It looks like the person who is resigning is not the one whose talk was rejected/downgraded, but is doing so because of the way the talk was rejected/downgraded.
The blog post states that the author will no longer be speaking at RustConf 2023 about a possible future for compile-time programming. The decision came after a call with RustConf organizers, during which the organizers informed the author that their talk had been downgraded from a keynote to a regular talk. The author initially thought the change was due to scheduling or finding a better fit, but later realized that it was because the organizers did not want the talk to be endorsed by the Rust Project.
The author explains that they had not initially submitted a talk for RustConf 2023 and had to register their talk after the deadline because they had not planned to give a talk until 2024. They were nominated by Rust Project Leadership to give a keynote about a Rust-related topic based on their previous work on compile-time reflection. The author emphasizes that their talk was meant to explore possible future directions and that the ideas presented were their own, not representing any official endorsement.
The author expresses confusion and disappointment at the sudden decision to downgrade their talk and the lack of direct communication from Rust Project Leadership. They feel that the decision reflects non-transparent decision-making and unprofessional behavior. They decide not to play along with the situation and choose not to give the talk in its downgraded form or negotiate for a keynote slot, expressing their disagreement with the behavior exhibited.
The blog post concludes with the author stating their choice not to participate in the conference and to refrain from playing along with the situation.