If you literally believe youtube videos for information about IT security, DON'T.
The only way someone could get your IP through League of Legends is if your P2P patching was on, and even then that's theoretically only when you're patching. Without your IP, and even with it, they can try to access all they want but it won't really put "your PC ... in their control".
Now, it is theoretically possible to force a crash of a Riot server just based on the IP. It's called a DDoS attack. It's also highly illegal and beyond the scope of just any random person with a PC. Further, Riot's servers most likely have at least some DDoS protection, so it's highly unlikely that a "drophack" would be effective.
More than likely, the people disconnecting were experiencing throttled internet connections due to high capacity on their network or other reasons. It's possible that the AFKs literally couldn't connect and didn't even try to come back.
Claiming drophack doesn't do much good - if anything send your network logs to Riot in a support ticket so they can look at what's going on, but they probably won't find anything.