Mancini is leaving Inter because Serie A is fixed.
Yeah, could be.
He has eyes, he can see that fishy things are happening.
Personally, i think he's leaving because he can't handle the pressure anymore.
His first two years with Inter were bad. In serie A he lost all the chances for the scudetto in January/February already while in CL his team was eliminated, first by their main rivals Milan (something Inter's fans can't forgive easily) and then by some CL minnows from Spain, Villareal.
Then Calciopoli happened and Mancini is convinced that Juve were cheating and he convinced himself that Moggi was the reason for his failures.
He finally got the chance to start winning big trophies with Inter.
And he did, he won serie A.
But when he expected everyone to praise him and Inter for the trophy they've been dreaming of for 18 years all he got was some underestimating statements where the scudetto was downplayed with the fact that Juve weren't playing and that the others started with points deduction.
The CL failure in 1/8 finals already didn't help him either.
2007/08 was a new chance for Mancini to prove that even when everyone starts from 0 and when Juve are also playing in serie A, he can bring big trophies to Inter.
Everything started well but then the papers started writing about the refs and how they've been helping Inter. They even didn't pick Mancini among the top 10 coaches in Italy.
And this is still happening. Every Inter win is downplayed.
Also, he probably saw by himself that not everything is as he thought it was and as Moratti has been telling him. He can see the offside goals, the dubious penalties.
He's been fighting with the journalists day after day but he probably realised that he can't win that war.
Finally, another early elimination from CL happened.
I guess he can't handle it anymore.
Fishy things happening in serie A, verbal wars with every sport journalist in Italy day after day , failure after failure in Europe, not being recognized as a good coach in his country even though he's winning a lot.
It was too much for him, i guess.