Think most teams in Serie A aren't really the most athletic and play at a slow tempo, although there are some really technically gifted players in the league. So a team like Atalanta that is well coached, young, and play a high tempo can blow teams away.
Hakimi will also put Inter in contention. He will create tonnes of chances for Lukaku. In Conte's system the Wingbacks are very important since Inter's midfield is not the most creative. Before this season most of the players he had in that role were pretty shite.