Here's some of what we've learned from the statement Ambassador William Taylor made to congressional investigators today. The entire statement is embedded below.
By mid-July it was becoming clear to me that the meeting President Zelenskyy wanted was conditioned on the investigations of Burisma and alleged Ukrainian interference in the 2016 U.S. elections. It was also clear that this condition was driven by the irregular policy channel I had come to understand was guided by Mr. Giuliani.
He decribes his slow realization that there was both a regular and an irregular policy channel -- the latter, made up of Trump's donor Sondland and Rudy Giuliani.
Ambassador Sondland said that he had talked to President Zelenskyy and Mr. Yermak. and told them that, although this was not a quid pro quo, if President Zelenskyy did not "clear things up" in public, we would be at a "stalemate." I understood a "stalemate" to mean Ukraine would not receive the much-needed military assistance. Ambassador Sondland said that this conversation concluded with President Zelenskyy agreeing to make a public statement in an interview with CNN.
Ambassador William Taylor Statement by Karoli on Scribd