Besides the fact that police come from slave-catchers and are an institution which should be entirely abolished, perhaps replaced with state-run SWAT teams for the scenarios that actually require an armed response and community safety officers for everything else, what you’re talking about is largely a result of the so-called ““War on Terror””. There was so much extra equipment from the Middle East that much of it was given for free to police officers. Military equipment plus military training (see “The Rise of the Warrior Cop”) resulted in police that view and treat America like a battleground and all citizens as potential threats.