Former world champions tend to have more recognition with today's audience. Nash was a champion in WCW and WWE, in addition to being a founding member of the NWO, so his resumé blows Jarrett's out of the water as far as the fans are concerned. I tend to not even count TNA since hardly anyone watches it. Might as well be an indy company. If this was 1999, then a track record in a rival promotion would mean something, but that's changed considerably during the past 10 years and TNA hasn't even approached WCW's buy rates (even from WCW's worst years). I doubt even AJ Styles or Samoa Joe would get a ton of reaction unless the show was in Orlando or Styles's hometown. I think TNA just seems to fans today that it's bigger and more recognized than it really is simply because it's there and it's technically the #2 promotion. And even that is debatable considering it hemorrhages money, whereas companies like ROH actually turn a profit (and sometimes out-draw TNA).
I acknowledge JJ did something historically significant when he founded TNA, but before that, he was the most overrated wrestler on planet earth. Both WWE and WCW blew him up simply because he kept jumping ship back and forth between the two companies. They had to make him look relevant just so the fans would treat his return as a big deal. Debuts always did well for ratings in both companies, even if it was a shitty wrestler like JJ.