Oh dear, I seem to have missed this thread.
Preeclampsia means the placenta is busted. The very first thing that happens in pregnancy is that the cells that go on to form the placenta implant, and in women who develop any of the variants of preeclampsia (PE, PIH, HELLP, whatever your care provider labeled you as having) that implantation goes wrong in a way that means that the mother's immune system has trouble tolerating the placenta.
They actually use the term "breakdown of maternal tolerance induction" a lot in the research papers. It means just that the placenta isn't able to coax the mother's body into a normal pregnancy. We - the human community, including the scientists who work on this - have frankly *no idea* how immune systems tolerate foreign organs through an entire pregnancy. And not just tolerate, but supply with oxygen and nutrients. With any other foreign organ, you'd see graft-host disease and rejection and dead people within a few days, at most, without powerful drugs designed to suppress the immune system. And investigating this scientifically is very hard, for practical and for ethical reasons.
No, it is not something you did. Promise.