We're all talking to things we don't really know here.
I'm an ex-helo guy, so I do know the deal on the low-level flying. If they were flying low-level for a legit reason, e.g. weather, terrain, training, whatever, and they happened to not catch the wires because of poor lookout, poor route study, etc, then this should be treated as an honest, yet severe, mistake. It does reflect poorly on the professional competence of the pilots and evaluations should reflect that. Should it be a career-ender? Not necessarily, but if your fuck up kills people, you can't expect to just say "my bad" and go on your way.
If they were low-level for flathatting, which I think is defined as "flying at low altitude and/or high rate of speed for thrill purposes" it is doubly bad. If there was no reason to fly low and they did, they were wrong. You can say it's something we do all the time, and that may be true, but again, if you kill people doing that, you're on your own. Now, this guy was the copilot. His culpability is about 1/100000th of the HAC's. Just because the HAC is dead doesn't mean he pulls all the weight for this.
In neither case does this represent criminal culpability, e.g. willful disregard for human life. Unless the testimony says that the aircrew raised objections and the pilots said,"Fuck you, we're doing this," it's not a criminal case.
There's definitely grounds for an FFPB/FNAEB/Coastie whatever, but criminal charges? No.