why is this the best move?


It's a weird one, especially as it can get kicked again there. You have to bear in mind that 'best' is relative. It also thinks it's your only 'good' move. It maintains the knight's presence in the centre, where it's strongest, for the moment at least. It creates no major catastrophe. That alone can qualify as best. But best isn't always winning, by any means. Sometimes it's just 'not losing.'