It was actually a miracle that Sexton lasted as long as he did. In Dochertys last season United played good, attacking football and we ended 6th with 47 Points in 42 matches (equivalent to 65 Points today) - and we also won the FA Cup. Leading scorers were Gordon Hill and Stuart Pearson both with 15 goals.
Despite spending close to a million pounds on Joe Jordan and Gordon McQueen - the results didnt improve and despite Hill being by far Uniteds best player in the 77/78 season - Sexton sold him to Derby (managed by Tommy Docherty) for £250.000. A move that did not go down well with the United-fans. United ended 10th with 42 points
78/79 was another poor season. There were some highlights - Gordon McQueen was a giant at the back and even scored 6 goals. And young Andy Ritchie scored incredible 10 goals in 16 starts. But United lost the FA-cup Final, and ended 9th in the league while suffering some nasty defeats in the process. (0-3 defeats to Everton, Bolton and Liverpool and 1-5 to Birmingham)
In 79/80 almost everything fell into place for Sexton - the signing of Ray Wilkins was a masterpiece and his 2 Leeds United-signings were both brilliant. Jordan scored 13 goals and McQueen scored an incredible 9 goals. Bailey in goal, Nicholl at left back, McQueen and Buchan in central defense and Albiston on the right. Coppell, Wilkins, McIlroy, Thomas, Macari and Jordan. And United came within 2 points of winning the league. But yet again, the strength was the defense - not the attack. United only scored 65 goals in 42 matches.
1980/81 everything fell apart. The first mistake was signing Garry Birtles to score goals - he was partnered with Joe Jordan up front. Jordan scored 15 goals - Birtles got none. Macari scored 9 goals, McIlroy 5 and Coppell 6 - but apart from that no player scored more than 4 goals. Wilkins got injured and only played 11 matches. Nikola Jovanovic which Sexton signed for £300.000 to replace Martin Buchan suffered from chronic back pain and only played 19 games before going back to Yugoslavia. The 7 wins at the end prevented it from being a total disaster of a season, but 51 goals in 42 was a tragedy. And after 33 games that season, United had actually just scored 37 goals. Defensively we were still solid - but we couldn't win football games. After 22 matches - we had won 6, drawn 14 and lost 2
So another £1 million had been wasted on a striker who didnt score and a football invalid - the fans hated him and we played the worst attacking football for decades. So yeah - there were a lot of reasons why Sexton had to go.