I think people who want him back are mostly "newer" fans who didn't watch him in the PRIDE days.
He was probably the most hated fighter on Sherdog (I used to have an account in 2004, made a new one recently).
Like Jones these days, but even JBJ haters can't deny that his exciting. Arona was perceived by 98% of sherdoggers as a boring Lay'n Pray artist. And a dirty fighter (see the Saku fight). And a whiny dude (he literally has an excuse for every single one of his losses). People also hated on him for (allegedly) being involved in dog-fighting with his best buddy Paulo Filho. And he didn't have much of a "personality"...
Very talented, and he beat a lot of big names in ADCC (never even lost a round I think), but most of his "fans" were trolls that always brought-up the Fedor fight (that he lost, look up the RINGS rules and watch the fight again)...
Also, his decision win over Guy Mezger was often brought up a one of the worst PRIDE decisions.
Seriously, he was TOP 5 in PRIDE (before getting blasted by Sokoudjou), but everybody disliked him. Of you were on Sherdod during his PRIDE run you'll remember that. That might also been because he was Wanderlei's worst enemy (worst than Rampage), and everybody loved Wand.
"Pride's Tito Ortiz" like they called him.
I can understand how new fans that look up his record could go "holy shit why did this guy stop fighting??? bring him back Dana!", but if you followed the sport back then, you'll get why...