Why Arsenal Won in the MKhitarian/Sanchez deal

So Manchester United and Arsenal just officially announced the deal of Sanchez and Mkhikitarian respectively, with Manchester United paying add-ons to United also, but most people think Arsenal lost in this deal but I don't think so. Selling a player whose head was no longer in the club and getting a world-class creative midfielder is a win win in whatever way you look at it even if Mkhitarian was frozen out of the United squad lately, let's not forget that this was bundesliga best player when he was still at Dortmund and linking Up with Ozil, Arsenal would create alot of chances and if they complete the deal for Aubameyang I see no reason why they won't make top 4.