Joe Barry is actually a Tampa-2 Marinelli guy.

He's landed with teams like the LAR who were running the Fangio scheme and is basically being told by MLF to run it. This scheme is handpicked by MLF.
I don't think it comes naturally to Barry. I also think Barry is one of those "Peter Principle" hires -- probably a good ILB coach but not a good DC.

Any pro coach who can qualify for a DC job can copy and run a scheme. IIRC there are (chunks of) old Fangio playbooks out in the Interwebs. I think you have to have a deeper understanding of the concepts, and also firm grasp on the finer points of it (e.g., why DBs have to line up at exactly X yards, etc.) in order to make it work.

There's also the fact that anytime a defense appears to be successful, it gets copied by other teams, and also deconstructed by offensive minds in the offseason. The Fangio defense is not doing as well this year because teams are starting to figure it out.