I think what we are seeing from the defense is real for 3 reasons -
1. DE/OLB upgrades -Setting the edge and rushing the passer - Dillon Harris & Kevon Jones at DE/OLB slots was a brilliant move. Gets sturdy, athletic players on the edge. These guys can run, tackle, rush the passer, or even dabble in covering the flat.
2. MLB/SS Upgrades - DJ Morgan and Diamond Harrel shore up the middle of the defense big time. They both tackle well and can run to the ball. Most importantly, they are smart. Whether or not they make the play, the other players can trust that they will be where they are supposed to be. This was not the case with last years MLB/SS options.
3. The pups are a year older/stronger and more aware - Travis Jones is a monster. Keyshawn Paul can tackle, and is lightyears ahead of last year in coverage and swagger. Lwal Uguak is playing the correct position( SDE, Rush DT).
What that all adds up to is a much more cohesive unit. Coverage is tighter, pass rush is more dangerous, and they are much more sound on assignments and keys.