Based on absolutely no evidence, I always get the impression that Conte is very strict with his instructions and it impacts the players negatively sometimes....in some cases restricting their freedom and creativity, in other cases imparting doubt and causing nervouness and lack of confidence because he does not really trust some of them.
I would imagine Stellini has been somewhat looser with instructions and also more senior players feel more empowered in Conte's abscence to make their own decisions.
West Ham are awful though so hard to read too much into todays result but will be interesting to see how it plays out.
I have compared it to when say your boss is overseeing your work or attending meetings with you - sometimes you go in to your shell slightly as you feel youre being judged continuously - worried youre going to do the wrong thing or do something he doesnt approve. I dont think Stellini is doing anything differently just perhaps the players are playing a bit more freely and without fear of reprisal.
The performance still wasnt great particularly in the first half but the players still attempted to be more positive which is pretty obvious.