Not only to they wither but those who championed the acquisitions declare victory then get promotions or move onto bigger and better things long before the acquired company gets integrated. Once the acquisition is complete, nobody cares any more, the patient dies and nobody is left to claim the body. If you probe with questions about how successful the acquisition was, it becomes an embarrassment and, so, the failed acquisition is silently buried with no fanfare and nobody coming to the funeral — — least of all those who championed the acquisition in the first place. I have seen this many, many times (not 100% of the time but more often than not) both having been on the acquirer and acquired sides of the table.