To be fair, she is relatively unknown.
Especially when you consider low information voters (which I expect have similar knowledge to high information voters from other countries).
Her honeymoon period will end as soon as she sits down and does a few serious and unscripted interviews about policy, which she has managed to avoid so far. At the moment it’s pure vibes, but at some point you need to get into the business of explaining what you would do and being challenged on it. That will generate lots of attack angles and media stories, both good and bad.
I get your point but hydrogen isn’t just sea water, you’ve got an awful lot more energy to put in after the “tank is full so wrap up the hose and drive off” stage to separate the hydrogen from oxygen to get the fuel. The difficult bit comes after “get water”.