What is the main reason for the failure of mergers and acquisitions?

The main reason for the failure of mergers and acquisitions is often a culture mismatch between the merging organizations. When two companies with different corporate cultures come together, clashes can occur if their values, beliefs, and ways of doing business do not align. This can lead to misunderstandings, conflicts, and a lack of cohesion, ultimately hindering the integration process and reducing the chances of a successful merger or acquisition.

References:

"Mergers and Acquisitions: Managing Culture and Human Resources" by Mark E. Mendenhall and Gary R. Oddou

McKinsey & Company articles on mergers and acquisitions