Proof? Because the competing narrative - police very reasonably includes McAfee in the list of suspects, and he's a paranoid nut from all the bath salts he's been doing, and possibly guilty, so he escapes - is actually simpler.
It was before the fire. The fire is more complex in your version, less in the one where the police are framing McAffee and getting back at him any way they can.
Otherwsie you have to concoct some story about how he paid a guy to go set a fire on his own property, for some dubious end...
I'm not saying one story or the other is true. Just the fire makes it more likely his story is true than before.
P.S. Just because you are paranoid does not mean they are not out to get you. Also I would suggest he has substantially greater experience with third world law enforcement than you do in your first world high horse.
Because houses occasionally catch fire even without any intervention from anyone
Unoccupied houses? You are the one skirting the realm of fantasy.
as opposed to simply doing its job and trying to round up a murder suspect
You'd know if he was actually a murder suspect as steps would be taken to extradite him.
why would they destroy their own property?
???? It's not police property.