I don’t think the name Manning is a factor, but the other two may very well be. Also, god for you for not thinking he deserves it, but did you feel the same way 2-3 years ago? I think Giants fans are just upset at him now..
I've always loved him for his calm demeanor, his consistently above average performance, and his nearly unprecedented durability. No doubt the Giants will miss all 3 in the near future. But never did I think he deserved to be in the HoF.
This is not an absolute rule, but for the most part, QBs in today's day and age that belong in the HoF are the ones whose teams you know should win 9-10 games or more every year, regardless of any other details you have on the team (i.e. Brady, Rodgers, Brees, maybe Luck (soon enough) & Big Ben, not so much Eli, Romo, Flacco, Stafford, Ryan, etc). Again, it's not a hard rule, but to me works more often than not.