There is the scenario that he would be frustrated or disappointed with players who maybe considered sub standard or seen to be unprofessional (drinking culture stuff etc) but by all accounts he (Ancelotti) can get tough and doesn't suffer fools.
I would imagine he's gone through the state of the club's playing staff and will make a decision based on what he thinks is achievable, what funds Lerner has promised etc. As I said earlier, some managers will see the club as a blank piece paper to write the footballing culture as they may like to have it.
Interesting that The Times has reported Rjikaard has contacted the club about the vacancy....if true that is.