The following is my analysis of the "politics" behind all this.
One difficult problem for Bartholomew is that there are two schismatic Churches in Ukraine – the Kiev Patriarchy (KP) and the Ukrainian Autocephalous Orthodox Church (UAOC). The current job of the two exarchs sent by Bartholomew is to talk with these two Churches in an attempt to reconcile them. The current head of the KP Philaret has the reputation of authoritarian and UAOC mistrusts him. Rumors say Bartholomew also mistrusts him. If the exarchs can't reconcile these two Churches, then Bartholomew will have to work with only one of them, most likely the KP.
When Bartholomew decides with whom he is going to work with, he will have two options. First, to proclaim an autocephalous Ukrainian Church. And second, to make an Ukrainian branch of the Patriarchate of Constantinople.
The first option is what the current President of Ukraine wants and he wants it soon, before the next presidential elections in Ukraine (March, 2019). Both schismatic Churches and the exarchs (who are born in Western Ukraine) are optimistic about the autocephaly, but I have the feeling that Bartholomew is going to disappoint them. Even if Bartholomew proclaims an Autocephalous Ukrainian Church, the autocephality is going to be meaningless unless the other Orthodox Churches acknowledge it. The President Poroshenko won't care who is going to acknowledge this Church, but Bartholomew does care. If the Ecumenical Patriarchate becomes the only Orthodox Church acknowledging the new Autocephalous Ukrainian Church, this is going to undermine the reputation of the Ecumenical Patriarchate and to raise the authority of Moscow – an outcome that Bartholomew wants the least. And since Moscow is going to break the communion with any Church acknowledging the current schismatics, the choice that any Local Orthodox Church will have is simple: Moscow or an Ukrainian Church which isn't even supported by the majority of the Ukrainian Orthodox Christians.
The second option is what Bartholomew pushes. If the new Ukrainian Church is not autocephalous but autonomous under the Patriarch of Constantinople, then nothing depends on the other Orthodox Churches. Moreover, Bartholomew already tried this once. In 1993 he acknowledge an autonomous Orthodox Church in Estonia much to the dislike of the Russian Patriarch Alexy II who was born in Estonia. For a while he was very angry and broke the communion with Constantinople, but then he accepted the situation and now we have the unfortunate outcome of two parallel Orthodox hierarchies in Estonia.
Some say that the current situation in Ukraine is analogous to the former situation in Estonia but this is not so. One difference is that the Estonian politicians didn't want an autocephalous Church. They only wanted an Church undependent from Moscow. In Ukraine the situation is different. The President Poroshenko wants an autocephalous Church and even if he changes his mind (as all politicians do), it is uncertain that Philaret (the head of the Kiev Patriarchy) will agree to this.
The most logical option for Bartholomew is to wait the presidential elections in Ukraine and only then to proclaim an autonomous Ukrainian Church. In this case the communion between Constantinople and Moscow will be permanently severed. Another unfortunate outcome of this are future hostilities against the Orthodox Christians who are under the canonical Ukrainian Orthodox Church. One specific of Ukraine is that most temples are not property of the Churches but of the municipalities so it is very easy to take the temples from one Church and to assign them to another.
Why did Bartholomew decide to act now, after all these years? He needed Moscow to participate in the pan-Orthodox council in Crete. But when Moscow decided to pull out, only days before the council Bartholomew was infuriated. Moreover, he is absolutely certain that Moscow is the reason that three other Orthodox Churches decided not to participate in this council. The Russian hierarchs tried to explain that there was no hidden plot to foil the pan-Orthodox council but Bartholomew doesn't believe. The irony is that in this case Moscow is completely innocent but nobody believes when they say they are innocent. (I am telling you this as a member of one of the Churches which did not participate in the council.)