For any phenomenon there will be a multitude of factors that caused the phenomenon. Therefore, any attempt to explain that phenomenon by invoking a single variable will always be wrong, and worse, misleading.
This is an exceedingly important element. We constantly look to change something by altering a single variable, then end up wondering why the results don’t change. It’s simple, though. No single variable, on its own, is responsible for any singl result. There are countless examples.