Russia Ukraine war, page-240993

In 2013, Yanukovich signed massive $10bn deal with Royal Dutch Shell to develop a huge gas field near Donetsk Lugansk regions. This was the largest deal that any ex-Soviet state has ever signed. I wonder why would the Europeans be dealing with such a "terrible leader". Obviously they considered him to be trustworthy

This deal would have resulted in Ukraine becoming richer, and Europe becoming less dependent on Russian gas.

All of that was sabotaged, after a US-backed coup overthrew a democratically elected leader, who actually wanted Ukraine to succeed as a whole.
By the way, he was overthrown after Yanukovich signed a deal with the opposition. However the more extremist, neo-nazi part of the opposition refused to honour that agreement, and proceeded to escalate the violence (Dmytro Yarosh).

After Yanukovich was illegally overthrown US handpicked an interim government. Donetsk and Lugansk declared independence. The interim government launched a war against independent republics.

That is how the hot phase of the conflict started. The prelude stretches back decades. But before we can move onto that, some people need to deal with their major memory issues first, because we are going around in circles.