Purdue also isn't the same program or athletic department it was two years ago. Purdue has some of the nicest facilities in the big ten, has invested over 100 million in the last two years, is paying Jeff Brohm good money, is planning more investments this next off-season, and about to announce a project to their stadium that will be worth at least 100 mil I'd say, the original was 150 mil. They are scaling it back to build it sooner. Plus Brohm currently has the #24 recruiting class with more 4 star guys potentially coming.
In order for Louisville to hire him this next off-season, they would have to pay petrino 12 mil to go away, then likely pay Brohm a 4.5-5 mil salary along with that same money in his assistant coach pool. That's assuming Purdue wouldn't match what they offered to keep him, which I think Purdue would match.
All that goes with a university remodel to the tune of approximately 2.2 billion I believe. This has all started in the last 2ish years. So not the same. Oh, and the Purdue fans are coming. Takes a bit to recover from not having a football program for four years.
As for Louisville, their athletic department is a mess. Why would anyone want to be a part of it? They just lost? a huge done in papa John and they don't get big ten money. Plus their path to the playoff is much more difficult. They get Clemson in their division. Purdue has beatable teams.