This is probably impossible to prove or disprove.
However, how do the authorities have experts prove a house was burned down by a rival urban gang arsonist who started it in one particular accelerant evident area in one corner of a room and know that smoking heap fire began there? They do it, though.
Two years ago Michael Savage of San Francisco believed Muslim terrorists were setting oddly configured fires. Not where the winds blew, the other side. Three or four in isolated areas without a power line drop near them. However, apparently the fires were mostly caused by the electric company. Now they shut down power if the weather looks windy and hot.
But look who has lots of experience with setting Molotov Cocktails on fire and deliberatly setting other fires in buildings in cities? Antifa and BLM wings of the Dem Party.
I’m seeing a report on FB of protesters blocking fire fighting efforts.