There was obviously a third scenario I never considered which may be what happened i.e. Ohtani is so dumb and disconnected from reality that someone could openly and obviously steal from him for over 2 years to the tune of 16 million dollars and he didn't know. I mean it isn't like it was hidden. Direct payments right from his account in huge dollar amounts. Still doesn't seem all that plausible given the amount and blatant nature, but there are a lot of morons in the world so maybe that is what happened here.
I have a story. Not precisely analogous but close enough to be worth recounting.
My dad was a pretty smart guy - and also (apparently) a trusting guy. He had just attained a new position and simultaneously had sold his interest in a business. I remember his exact salary when he started this new executive job because it was public: $27,500. The sale of his business was to be paid in annual payments of $20k per year for 15 years. So his annual income was just a touch under $50,000 - that was in 1972. So, not exactly analogous to Shohei money, however, my dad, my mom, and their 5 kids thought we were rich. And our thoughts weren’t too far off - that was a pretty comfortable household income in 1972.
Over the next 7 or 8 years, he entrusted his secretary to take his weekly paycheck and deposit it into the credit union account he had in the building in which they worked. The tellers knew my dad and knew his secretary. What my dad unfortunately didn’t know was that the secretary pulled a small amount of cash out of the deposit every week - for years. It was enough to accumulate to about $25,000 over the years, but - due to my dad’s poor oversight wasn’t discovered for a long time. Basically, he’d check his balance every once in a while and i guess it seemed to him in the right ballpark. If you knew my father you’d understand that his focus was elsewhere - a diligent and committed worker, but not so big on organizing the home finances. Anyway, eventually he became aware that something seemed screwy and he alerted the police who investigated and eventually charged his secretary with theft. She was found guilty.
Point being that smart people are capable of doing not smart things - like trusting people and not paying close enough attention to details. Doesn’t make my father or Shohei dumb people, just fallible people vulnerable to being conned by someone they trust.