Because this was simply a test to prove whether or not the systems worked - they wanted to prove they could meet / exceed a Mars orbit. They did exactly what they intended to.I don't get it, every one is having fun or joking but, if the goal was to orbit Mars and now you have missed, isn't that a failed mission?
Remember, this was the very first test of their new heavy lift system, and it was a resounding success. They had to prove the system works - and it did - and now they'll continue refining it.