Gatling guns aside, he was offered and turned down the use of other Cavalry troops (maybe the 2nd Cavalry, but I forget) so that his 7th could get all of the "glory" from the victory. More troops and guns would have been useful. He supposedly told his Crow scouts that he was going to be the new Great White Father when he won the battle, and the Democratic Convention was going on at the time of the Battle and for four days afterward. It is possible that a glorious victory could have led to his being nominated - or if if not replacing Tilden, then as his VP. Even if Custer could not have won, that does not mean that Custer did not think he could win. He thought greatly of himself and his destiny.