M&A is driven by the Financial Planning and Analysis corporate team in my company.
However, the in-house FP&A team has other responsibilities, such as monthly reporting and analysis and budgeting, and is not dedicated to M&A alone.
Therefore, it is complemented by external advisory teams in various stages of the M&A.
For PMI particularly, external advisors provided templates and general governance tools to guide the process, but PMI is primarily driven by internal functional leads with intimate knowledge of the companies.