The conquest itself only lasted 100 years or so, I think. And I have heard the Egyptians pushed out the Hyskos by adopting Hyskos bronze making techniques which would have probably made it easier to build pyramids, if anything. Yet no pyramids got built!
It looks like most of the pyramids were built prior to the Hyskos conquest around 1600 BC. I wonder if post-hyksos Egypt was somehow (for a long time) too economically traumatized to build any more pyramids. What do people think?
There's always more to be said on the topic, but I wrote about this in Why was there such a long period without the construction of pyramids in ancient Egypt? Khendjers reign was around 1760BC and and the next pyramid wasn't erected until 721BC by Piye?