I know of several people that voted for Trump. They live in an area where the economy isn't great, but they aren't in any way economically desperate (one is mildly wealthy, another in a household with more than double the local median income, excellent benefits).
Did people who feel left out give Trump his margin? I think they probably did. Are they his only supporters? Hell no.
I know a slew of people that voted for Trump. Many are in their 20's and 30's and have been treading water since finishing college. Many more are a lot are older and solidly middle class or upper middle class, but are watching their children flounder.
While the people you mention might not be economically left behind, they don't have a voice in the US media. _That_ is monopolized by the left (as evidenced by the article we're commenting on). There are other ways to be "left behind" than economic. Media is power, it was used against half of the population in the US; they didn't like that.
Did people who feel left out give Trump his margin? I think they probably did. Are they his only supporters? Hell no.