Nothing But Thieves have always denied the allegations against them, and to my knowledge, there's no firm evidence of them doing anything illegal. That said, there is a lot of testimony, from a lot of different people, about them being very into teenage girls, typically in the 16/17 range. They've had gigs cancelled and their support acts have left their tours before over it.
You can browse some testimony, including screenshots of DMs the band have sent to young girls, in this Twitter thread for yourself and make your own mind up. But it was definitely more than just one person looking for a payday. How would such a person even get paid in this scenario? There's no money in it, the only reward you get is abuse from fans who don't want to consider the possibility that a band they have a parasocial relationship with might be less than perfect.
It has blown over, mostly because the industry isn't interested in dealing with the power dynamics between bands and young fans, because many people don't see any problem with that dynamic as long as the girl is 16, and because NBT probably aren't quite famous enough to be turned into bait for prolonged tabloid fury. If they worked for e.g the BBC, they'd have been mauled and it never would have died down.