Background: Yelberton Abraham Tittle Jr. (October 24, 1926 - October 8, 2017), better known as Y. A. Tittle, was a professional American football quarterback. He played in the National Football League (NFL) for the San Francisco 49ers, New York Giants, and Baltimore Colts, after spending two seasons with the Colts in the All-America Football Conference (AAFC). Known for his competitiveness, leadership, and striking profile, Tittle was the centerpiece of several prolific offenses throughout his seventeen-year professional career from 1948 to 1964. Tittle played college football for Louisiana State University, where he was a two-time All-Southeastern Conference (SEC) quarterback for the LSU Tigers football team.
Context: At the time of his retirement, Tittle held the following NFL records:  Tittle was the fourth player to throw seven touchdown passes in a game, when he did so in 1962 against the Redskins. He followed Sid Luckman (1943), Adrian Burk (1954), and George Blanda (1961). The feat has since been equaled by four more players: Joe Kapp (1969), Peyton Manning (2013), Nick Foles (2013), and Drew Brees (2015). Tittle, Manning and Foles did it without an interception. His 36 touchdown passes in 1963 set a record which stood for over two decades until it was surpassed by Dan Marino in 1984; as of 2016 it remains a Giants franchise record.  Despite record statistics and three straight championship game appearances, Tittle was never able to deliver a title to his team. His record as a starter in postseason games was 0-4. He threw four touchdown passes against 14 interceptions and had a passer rating of 33.8 in his postseason career, far below his regular season passer rating of 74.3. Seth Wickersham, writing for ESPN The Magazine in 2014, noted the dichotomy in the 1960s between two of New York's major sports franchises: "... Gifford, Huff and Tittle, a team of Hall of Famers known for losing championships as their peers on the Yankees--with whom they shared a stadium, a city, and many rounds of drinks--became renowned for winning them." The Giants struggled after Tittle's retirement, posting only two winning seasons from 1964 to 1980.  He made seven Pro Bowls, four first-team All-Pro teams, and four times was named the NFL's Most Valuable Player or Player of the Year: in 1957 and 1962 by the UPI; in 1961 by the NEA; and in 1963 by the AP and NEA. In a sports column in 1963, George Strickler for the Chicago Tribune remarked Tittle had "broken records that at one time appeared unassailable and he has been the hero of more second half rallies than Napoleon and the Harlem Globetrotters." He was featured on four Sports Illustrated covers: three during his playing career and one shortly after retirement. His first was with the 49ers in 1954. With the Giants, he graced covers in November 1961, and he was on the season preview issue for 1964; a two-page fold-out photo from the 1963 title game. Tittle was on a fourth cover in August 1965.  The trade of Tittle for Lou Cordileone is seen as one of the worst trades in 49ers history; it is considered one of the best trades in Giants franchise history. Cordileone played just one season in San Francisco.
Question: Why was this trade seen as one of the worst in history?. Whats the answer?
He made seven Pro Bowls, four first-team All-Pro teams, and four times was named the NFL's Most Valuable Player or Player of the Year: