Ouch!!!!! Hopefully they had good insurance. We had a Marina fire a couple summers ago, but these boats were occupied at the dock ... I think we only lost 4 that night. Shame to see beautiful boats destroyed.
I don't know about other places but I have had things happen to my trailer while parked in at public launches. Tires cut, winch straps cut up, wiring pulled lose and so on. One of the reasons I am now at a private marina and don't have to launch. I have all ways guessed its jealous people and I suspect that's what is behind those fires.
As a boat owner on the illinois river I can say we are at a state of heightened awareness. There have been a couple of suspect fires and I hope we find the source before anyone else suffers any loss. and with the case if insurance, you do not always get total losses replaced without having to add additional money on your own. I know for a fact, (baised in losses of friends) my insurance will not cover all I have invested.