No finding has been made that they violated anything, nor is there anything suggesting that they "probably" violated anything. The article you linked to says that a radical left-wing group called Common Cause
filed a complaint with the FEC saying that in their opinion, a violation has been committed. It means absolutely nothing at this point.
This wasn't an action instigated by the FEC because a professional decided that there is probable cause to believe that something happened. This is more akin to a neighbor who was angry at not being invited to a party weeks earlier calling the police and filing a false noise complaint.
Finally, the equivalence is that Obama used the data outside of the Facebook developer TOS at the time, which stated that the data acquired through the API was supposed to only be used for the operation of their apps. By all accounts, including celebratory news articles sourced directly from campaign staffers, they used that data in violation of the developer TOS for campaign strategy and ad targeting purposes - with great effect. ~199 million people that did not authorize Obama to have their data had it handed to him anyway, for the express purpose of defeating a candidate that about half of them wanted to be President. I'm not sure how that's not far worse than the CA situation.