Why do girls end up going on a dick/hookup spree with other guys after they are dropped/ghosted by their “chad?”

That which is easy to attain is valued lowly for men.

Not a good generalization. Obviously supply will play a role in the perceived value of activity X, but there are plenty of things that even in high supply (think drugs, stimulating media, hyperstimulating foods, SEX) barring ridiculous extreme circumstances will always have a high perceived value relative to most other things. And this goes for both sexes not just men.

He just forgot women and men have different value systems.

huge generalization. not all men subscribe to the same value systems, nor women

It wasn’t an autistic question at all.

The question was:

if it’s so easy for them, why do they value it?

My response is, as anyone's response should be: because it feels good. People value things that make them feel good, and engage in activities that bring them pleasure. Sex is fundamentally (aside from drugs) the most pleasurable activity we can naturally participate in so it came across as totally autistic to try and overanalyze why a member of a sexually reproducing species would possibly feel the inclination to get dicked all the time