Here's what DeCourcy said in a radio interview when the host asked him about why the ACC was going to be tougher for Pitt and his response was pretty much this. I don't know what people will think, but this is his reasoning:
1. Previously, the BE's footprint was such that you were recruiting regionally (Philly, NY, NJ) and not really straying from there. In general, for a school like Pitt, you're going to walk into most kids' houses being, like, their 7th-8th choice behind the elite schools and the local schools right off the bat. For Pitt, they could go into those regions and hit those kids hard and develop relationships while the elite schools were chasing the national All-American types. Then, you could chip away at a school like Seton Hall or Rutgers or a downtrodden Maryland or Penn State by playing the "look at all the games we'll play in NY, NJ, and Philly, being local doesn't matter because we will have so many games in your area just due to scheduling". So, Pitt could pitch the Garden and the BE to kids and overcome the "local" factor that Rutgers and Seton Hall had over those NY/NJ/Philly kids.
2. NY basketball has died. Plain and simple, it's really been struggling. Lance Stephenson is the only NBA player to play in the NY public school leagues. That's amazing.
3. In the ACC, Pitt loses their "stay local, even if you come to Pitt" with the NY/NJ/Philly kids. Their focus shifts more to the Maryland/Virginia area for kids, and are facing the same challenges as before. They're probably walking in already being behind the elite schools and the local schools, but now if the kid wants to stay local, they are in a much more heavily contested area. You don't have the Rutgers/Seton Hall/Penn State type of schools around anymore, now you have Georgetown and Virginia Tech as the 2 weakest teams in the power conferences in the area. You just simply have more schools that are much more viable "local" schools in the DMV area. Corey Manigault was a legitimately strong get this recruiting cycle, having an offer from Georgetown (among others).
Essentially, Pitt had an easier time beating out local schools and pitching kids about "staying local by way of picking a BE team" in the Big East when they were fighting SHU and RU than they do now.
Personally, I think there are other issues outside of that (IMO, they used to do a really good job of identifying likely "Plan B" kids for elite schools and just hounding them -- they'd build a rapport and then if the elite school struck out Pitt still had a shot at landing the Plan B kid over them), but I wouldn't be totally dismissive of the shift in region either.
As KOAMB sort of gets at, Pitt doesn't recruit nationally and probably won't ever have a truly national presence. Few schools do.
