I'm personally convinced his long term, possibly unspoken, goal is mining asteroids. Getting a foothold on Mars seems like a logical, and necessary next step after SpaceX.
He does have competition: https://en.wikipedia.org/wiki/Planetary_Resources
He does have competition: https://en.wikipedia.org/wiki/Planetary_Resources
Some pros to having a base on Mars could be families of miners can live "close by" miners (or those that operate and/or maintain the telepresence or self driving mining equipment, and possibly a place to do any sort of processing.
Also, there could be mining possibilities on Mars as well, and without all the environmental issues we'd have to consider on Earth.
The "all of the eggs in one basket" aspect is certainly one I can get behind, but I think there's monetary gain is probably a more powerful motivator to those that have the most influence.