It's LLMs' generalist skills. I think reverse engineering is usually hard when you're in an unfamiliar domain. Eg I've never programmed a videogame or windows application but I'm trying to crack one. On the other hand if you know the domain, and know what the programmers' intentions must be in any given block of code, it's often straightforward. There are no unfamiliar domains for LLMs, including it seems proprietary software.