Did you read the WSJ article? https://www.wsj.com/articles/the-tech-whiz-behind-vine-and-h...

The reporter basically insinuates that Rus had been aggressively trying to undermine and get employees to turn on Colin for a year and leaves an open question on whether stress resulting from their toxic relationship contributed to him increasing his drug usage.

Basically, it was maybe not a complete accident unrelated to his work.