The start-up workplace culture was worse, work life balance was worse, the loud open-plan office was unhealthy, distracting and frustrating to work in.
Even on a generous expected value basis, favoring only high valuation exits or IPOs, and even as a super early stage employee, the compensation was way worse at the start-up compared with a stable high salary, bonus, retirement plan, and benefits.
To be clear, that is even if you assume away a lot of the risk for bad outcomes at the start-up and favor high valuation possibilities. Even still, the equity is manipulated by founders and investors and is so drastically unlikely to work out in a favorable way for employees.