He explained it multiple times on TV before and after WM, so I'm not sure what is confusing about it. The title (and therefore being the top guy and reclaiming his spot from Rock, who surpassed him in his absence) meant everything to him and he'd do anything to have it, even selling his soul to the devil.
It was the right move then and I think still the right move now. Austin's character as a face had done everything he could do and was stale even after a year off. One of the many things the Invasion ruined was Austin's heel run, even if he had some amazing comedy shyt and matches during it. Austin was getting legit heat, which is pretty amazing after the previous 3 years, similar to the way Bryan is getting legit heat today.
It was the right move then and I think still the right move now. Austin's character as a face had done everything he could do and was stale even after a year off. One of the many things the Invasion ruined was Austin's heel run, even if he had some amazing comedy shyt and matches during it. Austin was getting legit heat, which is pretty amazing after the previous 3 years, similar to the way Bryan is getting legit heat today.