Why are so many colleges suddenly free [tuition] under 200k?

I am also a little surprised since the Princeton NPC (as well as the actual financial aid package awarded) were the most generous out of all the meets need schools that my daughters considered. I would have thought this summer’s announcement would have led to even more generous packages, but every family’s finances are different so I am sure it depends on the specific mix of income, assets, and number of siblings in college.