As noted, PDs aren't going out and buying this kind of military equipment, it's being passed on from the real military. There is a correlation in some minds that equates defense spending with patriotism, and the DoD takes full advantage. [As do the contractors.]
If the DoD got the kind of scrutiny every sitting potus [especially the current one] gets, we'd be better off, I think. Once we got over the shock, of course.
Just as a contrast, one of my facebook favorites is Chief David Oliver of Brimfield, Ohio, aka Cheep Otter. Chief Oliver is a Mayberry kind of guy, who hands out 'tickets' [good for a free ice cream cone] when he catches kids wearing a helmet while biking. One little guy was so happy to get a ticket, he said "I LOVE Cheep Otter!" and the name stuck, lol. [I love Cheep Otter, too, and have a t shirt that says so.]
Chief Oliver writes a folksy bit every now & then, describing policing from his viewpoint. Brimfield isn't a big city,but the problems include meth dealers and other major bad guys, and the Chief does a lot to explain how that impacts the law abiding citizens, and why he does what he does.
It's a nice counterpoint to the militarization of so many PDs, and a reminder that they aren't ALL "SEAL Team wannabees" - though I suspect the ones that are, are in the majority. And why not? It's [basically] FREE stuff, right?
Except it isn't: we [taxpayers] paid for it. A lot.