This cultural divide has existed in Washington for a long time - but its not really a King County/not King County split - it has more to do with the Cascades. I'd also suggest that the outlying counties are not as broke as you seem to think they are.

Western Washington was an extractive economy that transitioned to manufacturing in the 20's and 30's - Eastern WA was and is primarily agricultural. It's a cultural divide that is usually pretty well bridged.

Why would you be afraid of Trump voters? They're Americans just like you are, and are trying to pick someone who'll solve their problems - which I'd note, are probably different than yours - a good reminder is, more people in King County voted for Trump than did in any other county, and King County accounts for 1/5th or so of the votes he got.