Is there a common thread between this years Free Agent Signings?

I started to think about the common thread between the FA pick Ups this year.Ayers DESmith LBGrimes DBConte SSSweezy OGAll are nasty and productive. I think this has more to do with a 'Cultural Change' especially on the defensive side of the ball (Are you listening Gerald). All are brought in as place holders, to be productive for 2/3 years, coach up their eventual replacements but most importantly, instill a sense of toughness and not accepting losing in any way!!! Opinions?