to do that he had to make sure the indians did not escape at the Little Big Horn
That's possible. Much has been written about his aspirations (especially in regard to the Presidency). The problem with that is it's speculation based mostly on anecdotal evidence. And we'll never know the answer since Custer's aspirations died with him.
Custer’s aspirations for Presidency should have been noted somewhere, especially in the St Louis Democrat Convention. But Dr Lawrence A. Frost never found anybody or any record which said that Custer had even begun a want-to-be-president campaign