computer analysis question

I am confused about the engine choosing move.

https://www.chess.com/analysis-board-editor?diagram_id=4137390 

So I won this game but according to the engine on move 10 I should have played

Qe3 

I avoided this because black can play Nxc2. However the engine does not even suggest Nxc2 which seems to me by far the best move for black.

so instead the engine suggests black play Bc5. but Nxc2 seems much better. How do I get it to tell me why Nxc2 was not better for black? Ok fine, I will assume the engine sees something I do not. 

I tried putting in the move myself,  Nxc2 to see why the computer would not play that and it just rebalances the analysis at even.  How can I get it to analyse my variations so I can see why what I thought was  the best move for the opponent (and the one I guarded against)  is not actually the best move.

sorry I realise I put this in the wrong forum