Meta has the capability to find out who authorized the change to this person's account. They log every change done in their administrator panel with a scary level of granularity, as far as I know, and they're able to take actions against employees who go behind Meta's back and take bribes (which, in joao's case, is what happened). This enforcement creates "waves" of account thefts described like so:
Suppose Mallory finds the contact information for Alice, an Instagram employee working overseas. Alice is paid next-to-nothing and wouldn't mind Mallory's extra cash. Mallory posts to their Telegram channel: "Instagram account takeovers for sale! Pay me $5,000+ and I'll take over ANY Instagram account". Mallory gets buyers lined up and promises to take over the accounts when Alice is working. The next day, when Alice signs on to the administrator tools, she sets each account's email address to the ones specified by Mallory, and Mallory pays her a percentage of what she charged. Mallory and Alice continue their scheme for about a week, when Meta finally investigates the situation, traces it to Alice's user account, bans or reverts every account Alice helped steal, and terminates her employment. However, no legal action takes place against Alice. Why? That part, I'm not so sure about. They're able to trace every action to Alice, and Alice is not anonymous, thus they have every ability to bring a case against her. Once Alice's employment is terminated, Mallory simply finds another employee willing to do their bidding. New hiring waves make this easy.
I'm happy to go into more detail about the underground Instagram account market. It's fascinating: people bragging about bribing employees and taking advantage of them, knowing their employment will be terminated, and actively showing off how much money they make. Meta has tried in the past to hit certain high-profile people with a cease & desist letter, but those are hard to enforce in certain jurisdictions.
