The Trump campaign worked pretty hard to make sure the new Republican platform won’t call for giving weapons to Ukraine to fight Russian and rebel forces. That's a pretty big change from the party's prior stance. I can only guess it's been engineered by Trump and his people and that certainly seems to point to Manafort.
Before Donald Trump went ahead and picked the man to lead his race for the presidency, Paul Manafort’s prior high-profile patron was previous Ukrainian leader Yanukovych. He was a stained applicant, and Manafort quickly facilitated his conversion into a successful individual. Apart from that, Manafort doesn’t have ties to Ukraine.
The current allegations are that $12 million in payments were earmarked for Paul Manafort by Ukraine. Manafort is named in a Ukraine anti-corruption probe. Still, there is no conclusive evidence that Manafort has influenced Donald Trump to change his view on Ukraine. People working on presidential campaigns have international associations. That does not automatically make them guilty when accused of wrongdoing.
I think Donald Trump changes his mind and his views to benefit him and only him. He now says he might recognize Crimea as Russian territory and lift punitive U.S. sanctions against Russia after he was strongly against this. In my opinion Manafort had nothing to do with Trump having a sudden change of heart.