prenups can and are often set aside if a fair settlement cannot be reached.
A case i had a few years ago had a pre nup protecting her 4.5 million worth of properties. They were married for 10 years (they lived in one of the properties covered by the prenup). She cheated and wanted a divorce she thought that see could keep the 4.5 million of the properties, take 80% of the savings and 50% of his modest pension.
(she does not work as all her income 150k+ comes from rental profits of her portfolio).
So the assists she wanted was
4.5 million of her houses
80% of their 100k savings
50% of is 150k pension.
(she tried to high ball him and apparently was willing to settle for 60% of the savings).
The judge set aside the prenup as the settlement would not be fair (aka she walks away with nearly 5 million in assists he walks away with less then 120k (with the majority of that being in pension fund so worth much less the assists and liquid money)
Judge ruled that he gets 1.5 million of the house portfolio, he gets 50k of the saving and keeps his pension pot whole.
(she still got most of the assists but it was much much fairer then what she was wanting/ suggesting as prenups are not water tight espically after a fairly long marriage 10years in this case).