I assume you've watched Lewis over the last few years. He has very little racing brain, and needs to be told what to do other than drive fast, wear out tyres and overtake. He's not one of the great drivers that can work out not only their own strategy and plan their race, but also work out other drivers strategies and races whilst driving.
McLaren said, just after his silly stop for Intermediates, that Lewis made that call. And they didn't mention he was having radio problems. That only came to light after the race, and I'm inclined to believe it as an excuse.