As someone who used to lead the IT side of a fair amount of mergers and aquistions, nobody buys a company without a plan to get a good chunk of value out of it over the actual price they paid for it.

It begins with the intent of the primary company. Some solely buy a busineas to resell it and then use thier expertise and resources to do so. There is almost always large inefficiencies in staffing, and a leaner payroll looks better on a balance sheet.

In other cases where a company acquires another the other commenter touched on which is it was purchased only for certain assets like customers. They’ll use the other assets if they can, including staff, otherwise they are written off.

And the most common one is where they want the company and all of the assets, but there’s a word that exec types love called ‘synergy’ - you see this a lot in low margin companies like retail. This is where there is a lot of redundancy and overlap between the two companies and they get the value by eliminating this redundancy and overlap, which pretty much guarantees staff cuts