**Spoiler** Collina leads Italian refs with 37% of vote and Webb with 42%?? Huh? I guess it's more competitive in Italy among referees, but I would expect Webb to be that much ahead of the other England officials.
It's timing and visibility. Webb is England's current #1 FIFA. He's done two of the biggest matches in the world over the past three years. He gets the big matches each week in the EPL. He's current and highly visible. Collina has been retired, I believe, for 7 years. His last international tournament was in 2004, at EURO. Since he's left the panel, Rosetti and Rizzoli have both had turns as Italy's #1. I would bet there are a significant portion of online poll voters who have never seen Collina actually referee.
I took a look at this site. It is ridiculous as far as US refs are concerned. It is supposed to be the last 25 years, but Mauro, Angeles and Baharmast all WC refs, are not listed, however Marrufo, Geiger, Salazar and Vaughn are?? Vaughn has now been removed (before his retirement age). I would guess that most people here would rate the former higher than any of the latter. Note that this not the case for Mexico, where several of their retired WC refs are listed, e.g. Brizio and Codesal. PH