” was simply too confident in his own abilities and often acted, ineptly, as his own campaign manager. “
Too many people hyped him, and he bought into it.
Walker has always been cozy with the GOPe and open borders crowd who were funding his campaign and propping him up as some kind of conservative wonder boy. That played well in Wisconsin against the virulent left, but when Walker couldn't keep the script straight that was handed to him, the mask came off resulting in low polls from Americans seeing right through him and his benefactors jumping ship who realized they were throwing in dead money.
He shot up in the polls after Rush praised him for a couple of days. That must have seemed pretty easy to him, thus the confidence. He never really pushed after that.