There are loads of such examples on YouTube, for example. They get into one account (say, OcUK). From there, they find your mobile number and call your provider and blag your email address and/or home address. Then they link those to find your social networks, then (maybe using dumped data or known exploits or social engineering) get into those and your email accounts... and it's all downhill from there.
Here's one quick demo. Once you have a mobile number, and an email address, or a single account login that has some personal info (such as an email address in the profile/settings) it's game over. It's possible to basically ruin your life and get access to almost anything. Enable. MFA. Everywhere.
I would hope that most of the frequent posters on this forum wouldn't fall for most of those tricks. You'd have to be really lacking in any security practices to fall for all of those.
Either way it's very interesting / eye opening. I'm pretty confident everything i use online is heavily locked down, so would be interested to see how far someone would get trying to get access to my data.