Presidential Pardons

So, I recently learned that the president can grant pardons to himself.

What were they thinking?

This gives a single person the freedom to do nearly anything he wants with relative impugnity. Think about it, as long as the president manages to plead guilty and be convicted before his impeachment trial ends, he's off the hook. The presidential pardoning power isn't limited by anything. It doesn't need to be approved by Congress, voted to be constitutional by the Judicial Branch, or anything of the sort. Not only can the president do whatever he wants politically, including bribing Congress/the Judicial Branch, but he can carry those powers outside of the government. He could easily make a robbery (Unrealistic crime for a rich person, but whatever), proceed to plead guilty, be imprisoned, and grant himself a pardon before Congress even thinks of voting on impeachment. In addition, he can't be stopped by violence outside of arrest, as using force would be assaulting the president, and so with a weapon he becomes nearly unstoppable.

Honestly, the possibility of something like this occurring is extremely remote, but it's still an interesting and dangerous possibility.