The only respect in which Nazis were left-wing was that they favored government intervention in the economy. But they weren’t in favor of other economic-left ideas, like labor unions, greater economic equality, worker’s participation in governing the economy, etc. In fact, they were violently opposed to such things, and the Nazis came into power in part by claiming that they needed to be in power to keep the communists from overthrowing capitalism. So it doesn’t make much sense to call them leftists even solely on economic grounds.
Extreme nationalism (like the Nazis, blaming foreigners and Jews for all their problems and wanting to kill or enslave all non-Aryans) is universally considered right wing, because the political right in general is considered more nationalistic (more in favor of war, puffing up national pride, blaming problems on others, etc.) than the left.