The recent Russian assaults in the Donbas over the past 48 hours have largely failed in every front. The Ukrainians apparently blew up a dam that forced the Donets River to overflow its banks, and there are videos showing the swelling waters trapping Russian armored vehicles, which were abandoned as a result. Still lots of reinforcements to come, but who knows if the Russians will ever pull off a decisive breakthrough in the east. This could be a slow, plodding advance that takes months, if the Russians last that long.
If Ukrainians are casually blowing up their own infrastructure like this, they're basically banking on NATO and EU funding their entire reconstruction either directly or by forcing Russia to do so. But there's no guarantee that either will happen.
The problem is that Ukraine doesn't have the capability or funds to rebuild any of its infrastructure. The reason Ukraine still looked decent from the outside (well, prewar) despite GDP per capita roughly the same as Syria is because they had trillions in accumulated Soviet era infrastructure that only required limited maintenance. It is FAR harder and FAR more expensive to build than to maintain.
Every building that is damaged, is a building that won't be rebuilt. Every piece of infrastructure that's destroyed, is another thing that Ukrainians will just have to live without. By blowing up their own dams
twice (once in Kiev, and now once in Donbass) it shows they don't care about their own infrastructure which is very unusual for a country fighting defensively, unless the situation was truly desperate. China only did this in 1937 against Imperial Japan.