Is the issue that he wanted to name his band Doomscroll or was the trademark attempt the problem? Plenty of metal bands don’t trademark their names. I just did a handful of searches against popular bands using some of my Spotify suggestions and found only a handful of matches. I bet he could have flown under the radar for a while until he got their attention, if ever. (This isn’t an attempt to excuse their behavior, it’s just an observation.)

I’ve been active in my segment of the metal world for some time and I’ve always had the impression that this isn’t something most bands do, especially when they don’t have an actual brand to protect! I’ve certainly never done it, never been advised to do it, never had a discussion with anyone else about it.