He might be a crook, but would he really be that lethal?
He cut off his finger, I think that's a little insane.
But when he left the estate his only crime was attempted fraud, he hadn't taken anything from the Carringtons yet.
If he started the fire for the money, i.e. being the only heir of the Carrington fortune then he had to be sure that the people who knew about the scheme (Cristal and Alexis) would die, but Alexis was going to handle the results of the DNA test.
He wasn't officially/publicly acknowledged as Blake's son yet, so Carrington-Atlanta and whoever it is who'd manage the Carrington inheritance (The Colbys?) may want to request some further proof. He wouldn't be the first long-lost heir returning to claim "his" fortune.
But even if all that stuff is irrelevant and he could claim his inheritance just-like-that, then there's still the question: why did Blake's son, and the brother of the groom, flee the scene just before or during the fire?
So if he did it, but not for the money then it was extremely cruel - was he that kind of person?
If he did it for the money then I think the plan is a little shaky.
Regardless, if
Hank dunit then I think it would have been better to
show it, and give us that extra instant kick that all of this is partially Alexis' fault. And does anyone think he's going to return after this?
The writers wanted to create a mystery, but they must have known that the fans would figure it out. Well actually it's kinda obvious,
too obvious. Suddenly I'm not so sure anymore.
There was no build-up to this whodunit, none of the other characters have very strong motives so I think they're going to bedazzle us with a complete new angle. The question is: whose angle?