Angus Primrose, while crossing the Atlantic in one of his very beamy designs was capsized, and was dismayed at how long she took to right herself. He later did some calculations and found that even a slight reduction in beam made a huge improvement in ultimate stability.
Again, boats staying capsized was never a problem, before excessive beam became the norm.
Brent, there are well designed boats and badly designed boats. These days very few are badly designed. Regarding beamy boats has I said, they have more positive stability (are harder to capsize) and when capsized require more energy to be re-righted. In the end it is all about the proportion between positive and negative stability.
Regarding ultimate stability considering that is the stability that is not used for sailing till the AVS point, you are wrong to assume that beamy boats have necessarily a bad reserve stability. Many have a a better one than narrower boats. I know, I have seen and studied many stability curves trying to understand that. In fact 10 years ago I used to thought like you.
Just to point you in the right direction have a look at this video:
This is a 40class solo racer, the boat that had inspired the hull of the RM, except that this one is a lot beamier. For 12m of length has 4.5m of beam.
You can see that he can recover from 180º without the help of waves just changing the water in his ballast. Obviously he cannot do that if the low CG, in this case high
is not helping a lot. In fact these boats have typically an AVS around 130º and have a huge reserve stability. That boat at 90º is making more force (regarding its weight) to get back to his feet than any cruiser I now off and I know a lot of them.