How can a small move make a huge difference

Queen Trading

Not a lot of 1500- rated notice it but the one who takes the first step to a Queen trade is at a bonus. If we look carefully, trading queens give a 75% result where the king ends up killing opponent Queen like this.

Successful Trade Queens
King Capture Queen
But the real question is that HOW DOES IT HELP?

Well you see, the one who took the first step to Queen trade actually denied the opponent's king to CASTLE in which case the Queen trader can castle As Soon As Possible!

White castles, black can't

Bishop, and a king can't castle

What is this?
Can you understand this very strong position?
This is a question only a 1700+ rated can answer! YES, with this black bishop piercing the board, it is preventing the king to castle. Here are moves where white tries its best but fails.

Queen attacking bishop
Black still prevents castle

Bishop
Still preventing castle