The Steelers had the first overall pick and inexplicably passed him up to take Gary Glick , who was at best a mediocre kicker before he then turned terrible in his second season (5 of 18 in FG attempts). Morrall's development was stunted by playing for three different teams in his first three seasons.
Buddy Parker arrived in Pittsburgh in Morrall's second year(1957) and within two weeks, he decided to give up Marv Matuszak and first rounders in '58 and '59 to get Morrall and Mike Sandusky. After a year, Parker decided he couldn't do without Bobby Layne, and gave up Morrall, a #2 in '59 and and a #4 in '60 to the Lions. The latter pick for Detroit ended up being Roger Brown.
With the exception of late 60-early 61, Morrall backed up Jim Ninowski and Milt Plum, but he finally took over as starter in 1963 and put up strong numbers, which George Wilson attributed to greater confidence, though he couldn't pinpoint any specific reason.
Wilson kept going back and forth with Morrall and Plum in '64, then new head coach Harry Gilmer dealt Morrall during training camp the next year, where he started for the crumbling Giants. Allie Sherman was looking for an experienced QB, and Morrall led them to a 7-7 record. However, the next year, he suffered a broken wrist at midseason with NYG already sporting a miserable 1-5-1 record that resulted in seven losses to end the season.
When the Giants traded for Tarkenton, Morrall again became a backup, and in the 1968 training camp, he was dealt to the Colts, with one early rumor saying that he was going there so the Giants could get the rights to Timmy Brown. Baltimore had supposedly given them a #2, but instead the Giants got backup tight end Butch Wilson, who had caught 11 passes in five years for the Colts and caught 14 in his two with the Giants.
In short, Morrall may not have been worthy of being the second pick in the draft, but he was able to play 20 years and avoided plenty of roadblocks along the way. Of course, I'm sure Don Shula considers him worthy of that #2 overall spot.