They lean left as a result of a higher standard of living derived from prosperity, not the reverse as you seem to be implying.
Such leanings are the self indulgent product of a booming economy, as are the arts, philosophy, public works, entertainment, etc.
Just as poorer countries are not poor because they are conservative, but are conservative because they ARE poor.
Contractions in the economy, even temporary ones (such as a recession), fosters right wing sentiments. Yes, left wing factions may holler for radical change, but that change always ends up falling back into the safety of tradition, the familiar, a retreat to a mythogical golden era where right was right and wrong was wrong and no one wasted time on frivolous decadent diversions.
You don't really think the current political climate and the rise of rightist elements is a result of fandom for a reality tv celebrity? The wave is worldwide, and has manifestred itself in the West almost rabidly in tandem with falling fortunes. Yes, meddling and prodding from homegrown to foreign elements plays a part, but they are dependent on a public dissatisfied with current directions and worried about a future with lesser prospects to plant their seed.
One day the oil will run out. Divisions far beyond today's silly little alt right/antifa left keyboard warrior fantasies will rise and descend upon each other. Billions will be kill each other for food, as in cannabalism. The few remaining will ultimately return to a medieval society, one permanently ossified by the simple fact that there will be no more resources to exploit, no place to steal them from. Socialism, capitalism, and whatever other distraction-isms will be the forgotten hobbies of a gluttonous past. Feudalism is what will coalesce out of the ruins the future. And that, will be that.