When the ACC signed its current deal, the SEC had the biggest TV contract. The ACC willingly took a smaller deal in exchange for a deeper partnership with ESPN. The ACC also forgoed the Big Ten's path of creating its own TV network. The only real alternative for the ACC was Fox. Fox provided a good deal but all things being equal ESPN made more sense from a financial and marketing relationship. What no one predicted is that the ACC deal would become antiquated less than a year after it was signed. First Texas got its own TV network from ESPN (the same company that talked the SEC and ACC out of TV networks). Then the PAC 10 expanded, got their own TV network and a blockbuster deal from ESPN and Fox. Most of those moves were defensive as ESPN and Fox didn't want NBC/Comcast encroaching on their territory of college sports. Since they were watching their peer conferences get rich, it was only natural for the ACC to ask for more. Expansion was a trigger, so the ACC expanded. But ESPN doesn't seem to have any more blank checks.
Since the PAC 12 deal, NBC has been less aggressive in acquiring college content. The NFL has also announced they will be showing games on Thursday night all season, which devalues ESPN's college football timeslots. Mix in the continued economic uncertainty and suddenly it looks like the ACC missed out again on a big pay day.
The ACC deal allows ESPN the opportunity to match any offers. So I assume this initial increase is an effort to placate and scare the ACC. I don't know how Swofford and company will play their hand, but I think they have to ask for more or reopen the contract. While it may seem like the ACC is operating from a position of weakness, bold moves (like the ones made by Big Ten, Pac 10 and Texas) have been rewarded in these deals. The ACC might be "down" but they still have some assets that won't change like Big TV markets, really popular national teams in football and basketball and the ability to play in timeslots that other conferences might not due to timezone issues or unwillingness to play on weekday nights. If ESPN or the other networks don't budge, start your own TV network. It has worked for the Big Ten and would finally make the conference truly stable and independent.