So I wasn't aware that these two weren't friends.. I thought they were on pretty good terms with each other, no? I must have missed something.
There was a really good profile of Calipari in a February (I think) 2011 issue of Sports Illustrated. I’d recommend it. There were two stories in the piece about Calipari and Pitino that shed light on the falling out. Each story is exactly the opposite of what was generally thought.
First, anyone who knows much about Calipari’s history is familiar with the “Carnesecca has cancer” story. Supposedly very early in Calipari’s career he stole a recruit for Pitt away from St. John’s by telling the recruit that Carnesecca (St. John’s head coach) had cancer and would soon be dead. That was the start of a lot of people not liking Cal - as the writer said, it allowed people to say Calipari would literally do or say anything to get a kid. The writer dug into the story to find the origin, and discovered Pitino (then at Providence) told other Big East coaches the story - from what could be found, the story started with Rick. (Eventually Cal and Louie would be very close.)
Second, for several years while Cal was at UMass, the commonly told story was Pitino had gotten the UMass job for Cal - vouched for him, even dug into his own pocket to help pay his first year salary. Every time UK played UMass that story would be repeated several times in some form. The writer again dug in. He talked to the AD at UMass when Cal was hired. He said the accepted version of the story was false. He said there were 3 people in the room, 2 of them wanted Cal - “and neither of them was Rick Pitino.” Said the idea that Rick cut the school a check to help pay Cal’s salary was nonsense.
They were thought to be really close early on, big brother little brother kind of thing. But there is animus bordering on hate now (and for the last 25 years anyway). I have no doubt there are stories going the other way, where Rick could point to things Cal has done. But that piece in SI made Rick look really bad.