Has it been said what the prediction was? I would bet a decent amount of money he predicted a 12 round decision and wanted to be proven right and therefore tried to carry Joshua through the rest of the fight. Probably saw that Joshua was so gassed mid-rounds that he thought it would be easily done.
Nonsense a professional fighter at that level does not let someone off the hook, especially when we all know how bad judges can be. If he had ko'd AJ there and then people would say old wlad is back UD (not guaranteed as the away fighter) and they'd say he got through on experience and smarts as the older fighter