I just don't believe that for 3 years Mizuhara directly transferred 17 million from Ohtani's accounts without Ohtani knowing (whether directly or via his tax professionals). Which matches Ohtani'a original statement that he transferred money to clear his friends debts (and then immediately changed that tune when he realized what that meant to his career). Mizuhara then took some responsibility so his good friend could claim he didnt know and continue his career (Mizuhara was going to jail anyway, adding on a few years to protect Ohtani makes sense).
I do not think Mizuhara was placing bets for Ohtani (though only 2 people knkw that). I think he did that on his own, I just dont believe for a second Ohtani didnt know that the money was being used by Mizuhara and what Mizuhara was using it for. But when Mizuhara is testifying under oath he stole the money and there is no other evidence it is an easy case to close.