That's what I originally thought, but after years of watching the Cowboys run the 3-4, I now disagree.
The 3-4 OLB, especially the Strong Side OLB, is a difficult position to play. I requires a 3 tool guy that can play coverage, rush the passer and be strong against the run. That's a difficult combination to find.
The 3-4 DEs are usually a minimum of 6-4, 295. If you take out all of the DL in this draft that don't fit that criteria, then you remove about 3/4ths of the players.
It's hard to find ILBs that are big enough to take on OGs consistently and also have any amount of coverage ability.
The 4-3 under that Marinelli primary uses, seems like the easiest to find player to fit. The WDE can be a smaller guy and you don't have to try to find a guy that is both big and super quick guy like you need in the Giants 4-3. The 3-tech DT can be a smaller guy than is desired for other 4-3s and for 3-4s. The 1-tech does not have to be a super big player like a 3-4 NT. The SDE does not have to cover like a 3-4 SOLB an therefore it is easier to find a guy that can stop the run and rush the passer without also having to play coverage.