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Depends what you mean
If why Hololive would choose to work with the Dodgers? Because they're in LA and a majority of the stuff Cover does in the US is with companies based out of LA or companies in LA. You'll also get a sparse bit on the east coast too. Plus Ohtani being a huge success for the Dodgers actually brought in Jap tourists to the US to watch some baseball, so there might be a small crossover of baseball fans and Holo fans.
If you mean why the Dodgers win all the time? They have a lot of money to spend, and unlike Football where there's a hard cap on spending (which they're usually middle of the road or worse) or Basketball where there's a soft cap (can spend more but just costs more, they are pretty good there), baseball is a free-for-all of spending. That's not to downplay their ability to pick players who will gel from the cream of the crop, but you're there to make money and win as a pro sports player, and if the Dodgers want you, it's one of the best options for both worlds. They do very little AAA farming unlike some of the other teams who do well picking up newbies and training them to be scooped up by the Dodgers if they're good enough. It's why you'll almost always see the Dodgers at the world series along with the Yankees.