why can toney,lewis?

why can those three stagger holyfield? but not tyson?. i mean if you watch tyson vs holyfield 1 round 5 tyson landed som good uppercut but it didnt bother holyfield and not in any point in that fight holyfield seem to get stagger or could knock down by any of tysons best shots. but vs toney round 3 toney landed righthand and followed up with combination, holyfield could fight for most of that round. and from then holyfield just be weaker and weaker. like vs lewis 1 lewis landed some nice uppercut seem to be as hard as the one tyson landed but holyfield looks like he got hit by a hammer. tyson and lewis uppercut seem to be even but tyson landed it harder. i have never seen holyfields face got blow up so ugly in any fight. almost worse than ali vs frazier. he didnt even looks like holyfield after that fight. so its the determenation? cause when holyfield fough tyson it was his time to shin, and he did won and got rewarded. looked like nothing could ko holyfield that night. vs toney he had chance to be cha,p again and in few early round it look like he gonna win, but got weaker only after some shots by toney...