I've seen it used a bunch but it was never explained what it actually means, assumed it was just some new millennial term.
It IS a new millennial term, yes, but basically it's just when someone gets their whole life/career wrecked, possibly permanently.
Sometimes it's famous people, sometimes it's normal people. Sometimes what they did wrong was clear, sometimes it's something that's subjective, but gathers enough steam to get them ruined. Sometimes what they did was malicious, sometimes benign but thoughtless. Sometimes they've apologized, sometimes they've doubled down. However, none of the above variables seem to matter at all usually, once the momentum starts rolling against them.