Manchester United, one of the most successful clubs in English football history, underwent struggles following the retirement of legendary manager Sir Alex Ferguson in 2013. After 26 years at the helm, Ferguson stepped down, leaving a legacy of unparalleled success, including 13 Premier League titles, 5 FA Cups, and 2 UEFA Champions League titles.

However, his successor, David Moyes, struggled to live up to the expectations set by Ferguson and was sacked just 10 months into his six-year contract. This began a period of instability for the club, with a revolving door of managers, including Louis van Gaal, Jose Mourinho and Ole Gunnar Soskjaer. 

Each manager had limited success but ultimately failed to return the club to its former glory. One of the primary reasons for Manchester United's struggles was the decline in the quality of the team's players. Many key players, such as Rio Ferdinand, Nemanja Vidic, and Ryan Giggs, either retired or left the club, while others, like Wayne Rooney, experienced a decline in their abilities. 

The club failed to adequately replace these star players, and as a result, the team's performance suffered. Another issue was the lack of a clear transfer policy and poor decisions in the transfer market. 

The club made several high-profile signings, such as Angel Di Maria and Memphis Depay, who proved to be expensive flops. Additionally, the club was slow to invest in younger, up-and-coming players and instead focused on big-name signings, many of whom did not live up to their hype.