the rules weren't put in place to protect those clubs, but entrenching those six clubs at the top was an effect of the tying of revenue to what clubs can spend. I do, however, think that the Arsenal, Liverpool, Man United of the world were hoping that they might slow down Man City (Chelsea to an extent but they were already miles ahead just looking at revenue). There has not been a sustained challenger to the "sky six", in fact only 3 teams outside of those 6 have qualified for the Champions League since FFP was implemented in 2011: Leicester when they won the title, Newcastle last season, and Villa this season.
I just had a look at the club accounts from the '09-'10 season and the gap in turnover from the 6th highest(City) and the 7th (Villa) is 62m.
the whole PSR losses thing is weird for me as well, as I'm pretty sure those rules (if they had hypothetically voted in), would not have counted until next season.