The term 'agent' should be taken with a pinch of salt in this situation. The person in question was an unpublished writer who built up quite a big following among other querying writers, and tended to be up to their (they've presented as female, male and NB as far as I can tell) eyeballs in unpleasant drama at all times. Lots of shouting about how awful agents are and how abusive the industry is, and much arguing and 'calling out' on Twitter. They started popping up on my feed for some reason, and I was always bemused about how many people seemed to view them as some sort of publishing guru. They went through 3 or 4 agents in quick succession - again, lots of drama - and kept taking Twitter breaks and coming back with a new account, claiming they were being persecuted. They talked a lot about supporting marginalised voices, but mainly seemed to shout at people on Twitter. They then started doing paid critiques of query packages, before announcing that they'd decided to be an agent.
Bizarrely, a small agency took them on as an assistant, then recently made them a full agent - only to sack them the next day after someone posted screenshots of a deeply unpleasant Discord server where this person and all their usual suspect friends had been mocking other authors, with one in particular coming in for a lot of nasty ableist abuse. More stuff about the server came out, and the agency apologised.
Many, many people then got involved in the drama, issuing apologies for having engaged with said person once, three years ago, by liking one of their tweets, and bewailing their own involvement. At least one of these people was then outed as having previously joined in the mockery of the exact author/book in question. Other people - including alleged agents - have been 'speaking out' about how awful it all was, while most of the publishing industry seems to be going 'Who? What?'
As far as I can tell, this is all confined to a fairly US-focused backwater of twitter, which appears to have no real connection to the actual world of publishing. It contains people who are, on the face of it, industry professionals, but who seem to have no actual clout, and, in same cases, seem to have little idea what they're doing. The agency in question seems to be tiny and doesn't look as though it's doing meaningful deals, and the decision to take this person on was so spectacularly bad that it has to raise some very big questions about their judgement and experience. The person who hired them is active in that part of Twitter, so must have known there were issues.
I think the real takeaway from this is something I've said before - people need to be really careful when submitting to agents and engaging with other people holding themselves out as well-connected professionals. There is no real regulation around literary agents, and the US in particular seems to have a culture of people just deciding to be agents one day, and taking on clients they have no realistic prospect of helping in any way. We don't have the same scale of problem in the UK as the industry is so much smaller, and everyone knows everyone else, but there are still a small number of bad players and people need to do their homework.