Comment by tialaramex

The squatters do a thing called "Domain tasting".

They buy domain X and then they put generic advertising, maybe keyword based, on a cheap bulk hosted site. They measure for a few days - is this bringing in lots of revenue? If not, they cancel the purchase, using a "grace period" available to users of the registry in case of mistakes - the purchase is unwound and they are refunded the fees. Domain X is now available again.

In principle this is forbidden for major TLDs but it's still possible and unscrupulous vendors help them do it, albeit it may now attract a fee if you do it enough that the TLD registry detects you tasting.

https://en.wikipedia.org/wiki/Domain_tasting explains about this and related practices.