Saw a video of a youtuber that got his account overtaken which has 2fa enabled (not sure which method but I'm thinking sms). He says he didn't get phished, downloaded anything and his session cookies weren't stolen and I believe him. The only clue is that he received a sms otp from google but was invalid when he inputted it which let's me to believe he relied on SMS for 2fa in the first place. My theory is he reused passwords and his number was overtaken but I'm not sure if that's the case since he did receive the google otp so that leaves out the common phone rep social engineering methods of porting out and fowarding. What else could it be? My paranoia is kinda acting up
Tldr: A YouTuber's account was hacked despite having 2FA. While unsure of the exact method, potential factors include relying on SMS OTP and the possibility of password reuse. No session cookies were stolen, nothing downloaded and no links clicked
Edit for timestamp: its kinda difficult since he jumps around a lot but he begins to talk about it around the 2min 30sec mark and stops at around the 6min mark
Concerning your edit: I've read that, too. That your connection drops, once a new SIM card gets activated. That might take a while, though, or not happen with some carriers or under certain circumstances. As far as i know a cell network is a crazy mix of technology. And from his description it's not even clear to me when he talks about SMS and when he talks about notification emails or push notifications.
And in other youtubers' videos I've heard they usually seperate their accounts so that it's not the same account for private stuff on their phone and the important youtube stuff all mixed in the same account.