His start here was absolutely crazy and honestly you can't hope for better goalscoring stats than that from any striker. And also, as Porque said above, him and Dembele have a great connection and he fits well into the team.
It's hard to see Lewa bettering the 6 months Auba had last season. If that stint hasn't been good enough to earn him a squad place then what is?
We always preach meritocracy but we don't practise it, the time he's spent here proves he deserves to play an important role, and it's hard to find players that fit in so well as he did. We are aiming to win all the titles and for that we need quality substitutes that ensure the level doesn't drop if a starter is missing. And if Lewa goes on a scoring drought, that we have an alternative.