The issue is that "whoever" isn't a single homogeneous entity. I would presume that someone in the organization spotted the discrepancy. Having worked closely with (and sometimes for) large corporations, I cannot presume that C-Suite decision makers were sufficiently aware of the issue. Or perhaps they didn't weigh the issue properly. Or maybe they were consumed by a desire to complete the merger, no matter what. There are quite a few ways this could have gone, internally, and still arrived at this place.
Anecdotally, I've worked at places where the due diligence process wasn't so much about determining if a course of action is good, but justifying a decision that was already made. If the subscriber count and income don't mesh, just use whichever number makes the merger look better.
