Thanks Franzdrake. Well here are the elements that i noticed before sacrificing:
1. Black king would be exposed (no pawn protection)
2. Possibility to bring all pieces towards the king for the kill (loads of lines opened) with this clear mindset: go forward
3. In the end, was sacrificing queen against rook, bishop and 1 pawn. So material is still balanced. I know this looks stupid, but that helped me a lot for taking the decision.
what about Bc6+ Nxc6 Qxc2. Black did not have to capture
Yes, I know Black did not have to capture but your line exchanges a Bishop for a rook. My line wins a rook for free.