I feel that kind of ad campaign is too controversial for Hollywood producers. They're using the Trump hat to sell a movie about the 1% gunning down the lower classes. Movie producers usually want to appeal to the broadest audience possible. This ad campaign doesn't. It's going after maybe half(?) of the U.S audience. That is why I think the producers behind this have some real chutzpah.
"Bible, Wrath of Khan, what's the difference?"
Stan - South Park
But the Purge movies have always been political in this way.
The first movie, the antagonists are bored rich white kids who are chasing down a homeless black man.
The second movie, rich people are literally paying poor people to come and volunteer to be murdered by them.
The third movie is about a liberal politician trying to become President to stop the purge because she sees it as class warfare.
It's established during the movies that the government is sending out murder squads during purge night to literally hunt down poor and homeless people who are seen as leeches on society - a rather clear parallel to Republican voter supression efforts.
They've been doing this all along, and the films have all been successful off of it. It would be weird if they stopped now.
Give a man a fire, and you keep him warm for a day. SET a man on fire, and you will keep him warm for the rest of his life...