I do believe the Bills "reached" for EJ for several reasons.
A few things to consider, Buddy Nix stated he was (finally) drafting a QB, come hell or high water. It is conceivable that the Bills needed a boost to sell season tickets with no baby in sight after 3 sucky seasons, and a QB drafted in the first round would help sell seats. EJ suddenly started moving up in the draft because of interest in him by several teams, and it was noted that Eagles new HC Chip Kelly was going to draft EJ the first chance he got.
Bucky Brooks 7 mock drafts leading up to the actual draft,
Although there was no QB in the 2013 draft that was actually graded as a first rounder save Geno Smith / Matt Barkley early on, in say March. Whats crazy is Geno Smith was the first overall pick by Bucky Brooks Jan 15 2013, and Barkley 7th to Arizona, Glennon 8th to Buffalo. * interesting note WR Robert Woods graded as the 27th pick in the first round at that time.
http://www.nfl.com/draft/2013/mock-drafts/bucky-brooks/155114
Then by Feb 20th Geno Smith is still the #1 overall, Glennon to Buffalo. Then on March 4th things changed with Geno Smith going #3 to the Raiders. Then in March 15th Geno Smith to Buffalo at #8. Then in April Geno going #2 to the Jags.
Then on April 24th Geno Smith dropped completely out of the first round.
http://www.nfl.com/draft/2013/mock-drafts
March 1st NFL's Mike Mayock's top QB's
Quarterback
1. Geno Smith, West Virginia
2. Matt Barkley, USC
3. Mike Glennon, N.C. State
4. Ryan Nassib, Syracuse
5. Landry Jones, Oklahoma
http://www.nfl.com/draft/story/0ap1000000146289/article/mike-mayock-alters-position-rankings-for-2013-nfl-draft
Lets face it, the only team that actually thought EJ was worthy of a first round pick were the Buffalo Bills.
http://www.nfl.com/news/story/0ap1000000158147/article/2013-nfl-draft-tyler-wilson-geno-smith-top-quarterbacks
Ej was graded as a 3rd or 4th round "project" before the Senior Bowl. The after the game he started moving up because all the rest of the QB draft class looked bad. Senior bowl stats for MVP EJ. 7 of 10 for 76 yards, one TD passing, one TD rushing. http://www.nfl.com/videos/nfl-senior-bowl/0ap2000000131256/E-J-Manuel-coming-into-draft-at-perfect-time
Then, http://walterfootball.com/scoutingreport2013emanuel.php
Now, all that said. This years team could have been so much better in terms of wins and protecting the QB if only they had done a better job with the LG position. EJ has shown flashes of brilliance at times, but he needs better protection and the offense to be able to run the ball in every game from the start.