when off the field it has become a personal matter and what is important is the game on the field that can make Chelsea win the Premier League this season. Aubameyang is a very talented player and scores goals. Half a year at Barcelona in the Spanish league and before that Aubameyang was also still in Arsenal's uniform. This is a reunion for Aubameyang to be able to appear again in the English Premier League but with a different club, Aubameyang uses the number 9 shirt at Chelsea. At arsenal, Aubameyang was captain and was able to score 29 goals from 163 appearances and this time when he was in Chelsea uniform could he score more goals, of course this is a new challenge for him.
I do not think that winning the title or not wouldn't be depending on Aubameyang and I doubt that he would be a decisive factor for how they will do this year. I am not saying he is an unimportant player or anything like that, he is good, but he is not team changing level of good anymore for sure, if he was then why would Barcelona even look for another player.
In the end, they got Lewandowski, who is actually a great player, and Chelsea had to wait for the last day, because they couldn't find anyone better and they were stuck with Aubameyang if you ask me. Of course he would be decent enough that he will be a striker that they needed, but won't be too much of a deal.