Not besides the official story, no. Based on just looking for a motive, I'd have a hard time believing it was anything than what supposedly happened, because why would anyone who's not a deranged cult leader just want to kill a bunch of people like that. I would be curious to see what's out there, though.

As for CIA ties to cults, though, the case of The Finders has a lot of pretty strange connections that I think are worth more scrutiny...