Because it was Lewandowski's wish for Barcelona and in the end they managed to play in LaLiga and compete with Real Madrid to be Barcelona's toughest opponent.
Lewandowski seems to have a good plan and he is a very good player even though he is 33 years old but for the next two seasons he will be fine and I would not expect his performance to drop with age but this is the love he wants to play at Barcelona.
Do you believe that this will be a threat to the future after Lewandowski is officially at Barcelona. Because after all the clubs in La Liga will be more careful to see the current Barcelona. For me, Barcelona is really consistent, even with the financial crisis, in saying that they managed to bring a dangerous player into their club. With the combination of these young players, it becomes Xavi ideal to further solidify his strategy.