[tptacek]

Without digging into whether you're right or wrong about this, there is a common pathology that happens where someone decides to leave, secures a strong offer, informs their manager, receives a counteroffer, and accepts the counteroffer instead of leaving. Many such counteroffers aren't really good-faith counteroffers (even if the company thinks they are); they are effectively "options" for the company to have you leave on their terms instead of yours.