Rudy seemed to handle the height and weight difference real well but Anthony was able to weather the storm until he got it to the ground where he was more comfortable. I think he wanted to trade blows until he saw what Rudy had and did the smart thing by getting it to the ground where he has the edge.
Excellent read, Rudy seemed to even man-handle Anthony at certain points to "shut down" the attempted takedown.
I think it may well have been a case of "over confidence" in his striking like you said, according to Anthony, Rudy certainly hits hard, it just that fighting a grappler tends to screw up your punches unless you spend alot of time training striking on good grapplers.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !