Is there a single reason?
I'd say that disruptions hurt national recruitng the most. The coaching changes, pot incident, and mid-season "fire Fulmer" stuff probably hurt recruiting with kids that weren't pretty high on UT to start with. They can't use the opportunity for instant playing time with as many positions this year either.
Those hinderances to national recruiting coupled with a down year for in-state talent and/or kids from other states that grew up with a Vol bias like Berry and Sawtelle... and you get a potentially tough year.
OTOH, if UT can land some decent recruits in the last two weeks it won't be anything close to a disaster.
If the class is ranked low because they take Scruggs and Raines plus some of the 3* guys that HV thinks might be underrated... I'm not going to get too worked up.
It would be nice to close out with a surprise from Davis, Thompson, Page, McClain, Abrams-Ward, and/or Witherspoon but CPF has a good enough record finding talent to give him a little bit of a benefit of a doubt.