KIEV, Ukraine — In the last five years, more than 13,000 people have died in a de facto war between Ukraine and Russia — a fight, many here say, to shake off the shackles of a colonial master and to move closer to the West.

A crucial figure in the effort was a billionaire named Ihor Kolomoisky, who spent millions of dollars to field and equip fighters and helped stop the Russian advance in 2014.

But Mr. Kolomoisky, widely seen as Ukraine’s most powerful figure outside government, given his role as the patron of the recently elected President Volodymyr Zelensky, has experienced a remarkable change of heart: It is time, he said, for Ukraine to give up on the West and turn back toward Russia.

“They’re stronger anyway. We have to improve our relations,” he said, comparing Russia’s power to that of Ukraine. “People want peace, a good life, they don’t want to be at war. And you” — America — “are forcing us to be at war, and not even giving us the money for it.”