Party strategists always say their party is going to do well. It’s part of their job. I don’t think this is particularly meaningful, unless you think there’s some particular methodology he has access to that’s better than Silver’s.
This is a perfectly succinct, textbook example of Outcome Bias.
Betting $1 with a 1 in 3 chance to win $2 is objectively a bad idea; the odds are against you. It doesn't stop being a bad idea if you win the $2 after 1 bet.
In one single election, yes. It means nothing, especially when you understand that his job is not to generate an accurate prediction, it’s to energize core supporters into donating to the campaign.
By the way, you can make the same argument in reverse—Trump always overperforms his polling right? If that prediction is accurate then Biden is absolutely going to get trounced. Now I don’t necessarily think this is correct, but it’s a slightly more sophisticated version of the fallacy you are falling prey to here.