It's all hindsight man. You obviously run the risk of making a mistake, but Ohtani strikes out 1/4 of the time - so yes, Ohtani is "dumb enough" to swing and miss at pitches off the plate. On the season, he had a 26% chase rate (62nd percentile) and a 33.4% whiff rate (4th percentile!). He was almost an auto out in the playoffs until the final game v. the Brewers.
Putting the tying run on base intentionally isn't some fail proof decision - especially with a guy who stole 59 bases last year. He can be in scoring position in a blink of an eye.
The probability of him hitting a HR there isn't actually that high (7.5% of all PAs in the regular season). We just ended up with the worst possible outcome of course. That's baseball.