Reagan was a union leader in the 40s and 50s, governor of California in the 60s, and elected president in 84 - he didn’t just go from acting to being president, he had a lot more political experience and track record than Trump.
Sure he had charisma and was a good public speaker, but that’s pretty much what got Obama the presidency as well.
LOX is liquid oxygen, which is not a fuel, but an oxidizer. Starship is fueled by liquid methane. Methane can not be made from just water, you need a source of carbon. On Mars for example methane could be produced from CO2 in the atmosphere and water from ice.