Why is this an inaccuracy? Please help.

I was reviewing a game when Chess.com flagged my Nc3 as an inaccuracy because I missed a better way to protect a pawn by playing Nd2. I presume this is to protect the pawn on e4. However, my Nc3 move protects that pawn but also the one on d5 and doesn't block a queen column. I can't understand why it's an inaccuracy. Can anyone help please.

Thank you for helping, but I’m sorry, I don’t follow. How does this show Nc3 was an inaccuracy. Following that trade, is white not a pawn up instead of down?

It's a complicated position.

Black has to play e6 either way to free their position. With Nc3, they get to exchange queens and simplify. This is followed by moves like Bb4 and Ke7 recovering the pawn. Getting rid of the N at c3 would simply further and weaken white's center.

Read my comments.