I think the same counts for a certain presidential candidate. A lot of people say he is just dumb but personally I think he has to be pretty intelligent to get to where he is.
The reason the world mostly works is because we all mostly trust each other. A relative handful of assholes and bullies will easily find ways to take advantage of that trust, but that doesn't make them intelligent.
You should passively improve with the amount of games he had under his belt, even if you put no conscious thought into why it is that you're losing or what you could be doing better. He performed at a level which is what, the lowest 10% or 20% of players? Many of whom were probably new to the game because most people will climb in rank over time.
That said, it's totally fine to play a videogame without any desire to be good at it.
More importantly studies on chess show that a tiny amount of skill (<10%) is explained by intelligence. I see no reason that MOBAs would be much higher, as in chess they are likely mostly memorization and practice.