Maybe at the post-draft presser, someone will ask Beane why Allen over Rosen or even Jackson and you'll get your answer.
A better question is if Rosen was rated the #1 passer coming out this year, why did he fall to #10 ?
http://www.espn.com/nfl/draft2018/story/_/id/23329508/josh-rosen-pissed-fell-arizona-cardinals-10th-pick-says-there-were-nine-mistakes-ahead-me