The Ukrainians have been trying since they achieved independence but decades of corruption from Soviet influences are hard to change. The same has happened in other Eastern European countries after the fall of the USSR. Change can happen slowly when it's deeply rooted.
It's no difference than the corruption that's deeply rooted in certain US cities that have been run by a certain party for decades.
The Ukrainians had their 2014 Revolution.
en.wikipedia.org
They voted for Zelensky in order to deal with corruption.
Volodymyr Zelensky: The Promises of Ukraine's New President.
impakter.com
Then the Russians attacked as a follow-up to the 2014 attacks.
In a fashion the current war is helping to root-out Russian sympathizers.
And it took decades for Japan & Germany to change after WW2.