I wonder if it has anything to do with the rise of e-sports and the monetary aspect of "professional" multi-player games?
That's one of my theories. Money got involved and here we are. Now games are serious business! Remember when they were just fun?
No, people cheat at multiplayer games that have no stakes pretty regularly.
This is more necessary with the rise of freemium games where the base account is trivially replaced and so banning people's accounts does nothing.
Not that paid games don't have cheating issues, but there's a limit on how much people are willing to spend getting rebanned regularly.