The Oakland Athletics lost Tom Underwood to then-reigning World Champion Baltimore Orioles and so the Athletics chose Belcher from the Yankees.
As the legend goes (from Baseball Reference’s Bullpen Wiki, as an example), “However, because of a front office mix-up, his name was left off the team’s protected players’ list for the free agent compensation draft and he was selected by the Oakland Athletics on February 8th. Yankees owner George Steinbrenner was livid over this development and blamed young general manager Murray Cook for it and fired him shortly afterwards.”
It is true that Steinbrenner was livid over the situation and he helped push for the elimination of the system after that year (the Mets also famously lost Tom Seaver to the Chicago White Sox in 1984, but that was just flat out incompetence by the Mets, who actively left Seaver off of their protected list, figuring no one would want to take an older player like Seaver.