I have just realized that this must be very confusing for non-Americans. Why are people just letting the cities burn?
It is because they are TWANLOC: those who are no longer our countrymen. We don't care.
Most of the people that just want to be left alone already moved out into the country a long time ago. So what's left in the big cities are majority nutso, dumb, and/or wicked. And they elected representatives accordingly.
I will piggyback on Larry Correia's excellent post, Where Are All You Gun Owners Now? The background is that those dumb wicked nutsos in the big cities have wicked amenable authorities. So we are doing the one thing that they would never expect and can't defend against, which is to keep on spooling out rope until they have enough to hang themselves with.
And in the meantime, let the cities burn.
We. Don't. Care.