For “leads” to drop that much it must mean they weren’t legitimate, happy leads in the first place. I bet those “leads” came from a shit letter popup or other similar dark pattern, in which case AMP works as designed and benefits the user by shielding them from such garbage.
AMP is bad for the web in the long term. But it is a decent stop-gap solution given that nobody is willing to make their websites bearable without Google’s pressure.
EDIT: I just tried their website again without an ad blocker and sure enough, I was asked to subscribe to their shitletter.