"Frankly," he said, with a bit less... politeness than thus far, "I do not care for whom or why you do it. It matters to me that you will be better than what exists now, and unless you plan on enslaving every non-human in the galaxy you are."

Seriously, why has always been the question he concerned himself with least. It's... a question for the future or echo of the past. It has little impact on now.

Also? He wants Palpatine dead.