He's also trying to completely go against the prophecy of the Cosmogony. He waited 2000 years to fight the Chosen King and kill him at full power. This is why Ardyn leads you to Titan, then to Luna, then to the Crystal, all to obtain power. He wants to make sure Noct has everything (the power of the six, the royal arms, and the ring) before tearing it all down.
I fucking love Ardyn as a result.