Head over to the link to see the four reasons the article gives.
But for collectors, expect Ohtani rookie cards to see a boost even before he bats/pitches his first Major League game.
There isn’t much out there for autograph card seekers at the moment except the ones from overseas like this one: 2013 BBM ROOKIE BGS 9.5 ORIGINAL CERTIFIED AUTO
But there are more of the 2017 Bowman Chrome non-auto cards on eBay. Here are a couple of higher end refractors with high grades.