The right basically has a monopoly on young men, making it very lonely on the left for young women.
Contrary to popular belief, young men can go monk mode for much longer than women can. Men aren't the ones whose literature consists more or less exclusively of romances, they don't play house when they're kids, they don't daydream about the wedding day.
Eventually the cuter girls started to realize that the predominately male political environments of the far right are a target rich environment full of very friendly young men who are quite happy to see them.
So they defect.
Cute girls defecting is a precursor to the preference cascade.
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C. S. Lewis