Citroen stated they targeted bringing in Ogier for 2018 (and so let Mikkelesen go to Hyundai). So they didn't think he wasn't fast any more, or soon looking to retire ...

Plus Ogier had the car advantage at VW, hence why he was fastest so often then. His 2017 Season and team was a whole new ball-game.

He is smart AND fast. That's why he's the Champion.