I'm one of the maintainers (https://github.com/sindresorhus).
If I can throw my second impression, what a little shit. But maybe I'm too much of corporate conformist...
What he's running up against is an all-too-apparent piece-does-not-fit-problem between the business model and goals of revenue-focused tech companies and the individual motivations of (some?) open source engineers to improve the world in ways that they feel are effective.
It's understandable that if you're building something and see a for-profit company building exactly the same thing -- but with perceived worse negative externalities than your own -- that you'd be a bit frustrated.
If that competitor really wants to capture the market (ignoring externalities) it's plausible that they'd compete with him and try to pull the market across to their own services. Competition can be stressful, especially depending on how well the players behave towards each other.
I have little doubt that it's legal advice (or a sense of legal advice) that is the reason why he didn't receive a response to his offer to collaborate (perhaps a hope that they would take some of the weight off his shoulders; not totally unreasonable for someone who is maintaining important software that many people rely on).
He's been involved in some peculiar stories in the past but for the sake of debate here I'd suggest trying to ignore that. I don't think this will be a unique story; it's the open source sustainability problem[1] and I'm not sure we have consensus on clear, effective solutions yet (perhaps there will need to be a mix of options available depending on individual personalities).
[1] - https://www.theregister.com/2021/05/10/untangling_open_sourc...
