Germany had the high-dollar prisoner that Putin had wanted back for quite a while, the rest seems to have revolved around that. Someone so awful that giving him up meant a big hit to their judicial/justice system. Of course they wanted their people back, all of these nations wanted their people back.

Discussion last night said that these negotiations had been going on for months, and that Alexei Navalny was originally part of the package. His release seems to have concerned Putin so much that he had Navalny murdered. Then the rest went forward. I haven't pulled the Wall Street Journal's apparently detailed article about the exchange, but it may offer more insight.