It's not the burning that directly leads to something better. It's more like a natural consequence caused by failing to adequately address people's need for something better; people who feel powerless in their quest for justice will treasure morsels of that justice whereever they can get it, such as direct attacks on the public institutions suppressing them.

The good that can come from it is motivation: it's more clear than ever that gradual reform is not occurring, and something has to change at a fundamental level. Enabling people to get justice civilly will sharply reduce the number of people resorting to incivility.

Well, it may not be the most constructive way of dealing with police abuses, but it's one of the vanishingly few consequences police have faced for their malfeasance and unfettered violence.