I think he believes this was his chance and only chance he had of getting Derby up. They had some really good players in Huddlestone, Raziak, Idiakez. Huddlestones gone, and the other 2 have been linked with moves and will most likely move on. These 3 were the backbone of his team and made everything tick so will be a massive loss without them.
I doubt he wouldve swapped all this for the Hearts job though, they are at the minute not a very stable club. He will have seen how they treated Robertson and i dont think he will have been impressed. I believe Hearts new chairman will turn out to be one of broken promises. A bit like when John
Boyle, i think his name was, took over Motherwell - he said how he would be spending big bla de bla...And looked what happened there.