The incel is fixated on the idea of seeing the people he most cares about and identifies with score with as many girls as possible. His hope is that he can succeed through them vicariously, and that if other people with similar (supposed) mental deformities can score, he should be able to as well. In short, him cheering them on and feeling visceral frustration at any hesitation they show is merely him confronting his own demons and not considering the other person’s feelings at all.
How selfish of him.