[FlameOn]

Timing on this coincides with Ukraine's decision to suspend all negotiations while Putin is still alive. Once that decision was made, the op to blow the bridge was set in motion by Ukraine.
Ukraine must have concluded they don't care about a mix of Russian speaking population in Crimea and most of the Russian forces would surrender rather than fight in the area/are willing to take those additional losses against Russian forces fighting with their backs to the wall in Crimea.

Here's a past background video on why they kept Kerch bridge around till this point.