He's a businessman. He wants money; he wants respect; he wants power. Like most businessmen/politicians/people of stature of that caliber, he's just couching it all within a story that's much more palatable to the general public than saying that.

Also, I personally have always found how Tesla fits into this Mars equation laughable: why are we building sprawling infrastructure that needs cars on Mars? Is his imagination limited to Atherton, but on Mars? A much better use of limited resources (and oxygen) to build infrastructure would be to build denser, walkable colonies with major corridors served by public transit. Electric light rail or self-guided people movers are not new or novel, but we all know how Elon feels about public transit.