This has only really come about because of the Der Spiegel articles and the hacked e-mails. UEFA opened their investigation, and the Premier League opened theirs seemingly off the back of the UEFA one. I think most of us thought - understandably - that when we won at CAS that that would also be the end of the PL investigation. However, it appears that certain clubs have been pressuring the PL into continuing to pursue this and it's kind of snowballed from there with a raft of charges that encompass far more issues and seasons than UEFA had us up on, even pre-dating the implementation of both UEFA and PL FFP, such as the Mancini stuff for example. What I find most surprising is that they've also chucked in all the stuff that UEFA eventually lost on at CAS - after that verdict I didn't think that the PL would want to touch any of that with a bargepole but I suppose they're winging that one in the hope of getting a different verdict to what we got at CAS.
I'm as certain as I can be that without the lobbying of certain clubs who shall remain, cough cough, unnamed, this wouldn't have gone anywhere. No doubt they'll have also chucked in threats about reviving the Super League idea for good measure in order to shit the PL up into doing something.