I assumed it was that the Wrestler had signed a contract agreeing to have their business interests managed by a certain entity, i.e. "Mr. Fuji Incorporated". In exchange for some of the purse, the manager agrees to protect that wrestler's general interests (including, but not limited to, transportion & lodging needs, match promotion, promotional materials including interview supplementation, "external bias nullification" - i.e. ensuring opponents will not try to use underhanded tactics to secure victories and general publicity). However, that manager could then sell their controlling interests in that entity to another manager organization, and hence " Mr. Fuji Incorporated" was now controlled by Sensational Sherri.
After giving this some thought, I'm not sure it's accurate. If a manager works for a wrestler, how can a manager fire a wrestler? We have seen this happen many times.
Furthermore, when a manager turns on his client, shouldn't he be held liable for breach of contract? At the very least, you'd think that'd be grounds for having your managerial license suspended.