I don't get it. It's 2024 and there are so many ways to legally bet on sports. Some pro athletes post their bets and betting results (for other sports, of course) on Twitter. The presence of an illegal bookie here has seemingly three rational explanations:
(1) The translator's second story is true: he was stealing money from Ohtani and needed to use an illegal bookie who wouldn't ask questions or report him to law enforcement
(2) Ohtani was indeed betting on baseball (something nobody has yet alleged btw, even about the translator) and needed to use an illegal bookie who wouldn't report him for this
(3) Either Ohtani or the translator were really worried about taxes and wanted to use an illegal bookie who would not report them to the IRS
Not to get political, but these were both people voluntarily living and working in California so I doubt they have too much of an issue with taxes. Put another way, they had easier ways to reduce their tax burden if that is what they cared about. So #3 is out for me.
