both aspects are relevant. Barca needs money and Aubameyang wants to get a place in the first-team squad. because Lewandowski will certainly make Aubameyang more likely to be a substitute. Of course, it wasn't good for him. and he's got a great place at Chelsea. it was a good choice because Chelsea needs him up front.
I didn't expect, this is a surprise. Indeed, if we look at Barcelona's current squad, perhaps their top choice falls to Lewandoski. But actually I think Aubameyang could be an alternative option, looking at Lewandoski's age who probably won't be long before playing ball.
Actually Aubameyang is good, he only got into trouble with Arteta when he left Arsenal. Maybe if he is right to Chelsea then he will reunite with Tuchel while together at Dortmund. Perhaps Barcelona have a lot of consideration if they are right to release Aubameyang to Chelsea.
Lewandowski is undoubtedly Barcelona's first choice for the central forward position. There are also Aubameyang and Depay to play in the same position. So I think Barcelona might decide to sell one of the two if they get a good offer.
Aubameyang can be his worthy replacement if Lewandowski is injured. Xavi may want to play consistently well. Therefore, if Lewandowski is missing in a match, it will not affect Barcelona's performance, so he wants to keep Aubameyang in the team as a replacement. However, Barcelona's financial situation is not good. So I think Xavi wants to keep Aubameyang in the team now but Barca management might be interested in selling him.