The original idea of ffp as planned by Platini was to deal with debt, which he thought was damaging and corrosive to clubs. He considered it grossly unfair that certain clubs could play in and win uefa tournaments while carrying huge debts. He mentioned the rags and Chelsea.
The ffp we have obviously bears no relation to that ideal, and concentrates on revenue streams, of which the elite clubs have many more than some others, and spending related to those streams which the elite clubs do plenty of.
What changed their minds?
I can’t think.