If it was a collective of people it is(might be) more likely that one of them is incompetent(and didn't configure TOR properly) where-as if it was a single competent/careful individual there's a smaller chance of a TOR mis-configuration and resulting IP-address leak.

I don't think it lends much credence to the 'multiple entities' theory at all personally, but that's the best I could come up with. Feel free to correct.