draw.io has moved from the .io domain in 2020 . Their arguments were precise and persuasive. After that I do not know why would anyone stay on there.
Given that all the dictionary word .com/.nets got bought out a long long time before many of these startups, started up, a lot of money needs to change hands.
I don't know anything about the history of these particular TLDs, but this page really comes off as 'hey we now have a load of money and can afford to buy the .net we always wanted but it's actually it's for a good reason and we're better than those other hip new companies' - kinda like 'my expensive personalised number plate is actually raising awareness for world peace - your standard one means you don't care' or something.
Again, I'm just a complete outsider here, but that's my initial reaction. Maybe I'm just jaded.
To be more on topic, to quote:
there was a security issue with the .io domain. In 2017, a researcher managed to take control of four of the seven authoritative name servers for the .io domain. We accept that mistakes can happen, strong processes limit the chances of them happening, but they still can.
However, the domain administrator made no attempt, at any time, to communicate with anyone about the issue.