I’m not sure I would consider that “hiding,” it just looks like they’re minifying/concatenating all their enqueued scripts.
A plugin like Better WordPress Minify could help although I don’t believe they’re using that because you can see the index of /wp-content/assets/ …meaning the files are actually in that location, not rewritten to use the /wp-content/assets/ URLs.
This suggests they’ve manually made a build process to include all their plugin CSS/JS, place it in files as @Andy_uxl mentioned above, dequeued all the original plugin CSS/JS, and enqueued the wp-content/assets/ stuff.
You can even plainly see the source files commented out in /wp-content/assets/js/all.js, which reveal references to plugins like Contact Form 7, some lightbox and modal plugins, etc. So again, that backs up the assertion they’re not attempting to “hide” anything. They’re probably just doing it for performance reasons.
It seems like a lot of effort just to “hide” plugins from your competitors but perhaps it’s worth it for the performance benefits.