One problem with the GOP's inability to understand or process populism is that it gets walloped by the all-populist all-the-time Democrats. Another problem is that when Republican populists do appear, they tend to be rather unfocused and undisciplined.
Political focus and discipline are very hard to come by. It takes a huge organization that spreads across both the political and private spheres to harness popularity and convert it into effective policy action. The Left spend decades building and refining its machinery.
The Left's machine spots populist talent early and begins guiding it toward politically productive ends. Detailed plans are made to move the country toward the populist's goals across multiple election cycles. Money and media influence is lined up to achieve concrete goals.
Achievable goals are important, because without them - and a serious political/financial/media machine dedicated to achieving them - populist crusades usually end in disappointment, resentment, and unfocused anger. "What was all of this FOR?" furious or dejected supporters ask.
Many of the Left's endless populist crusades seem kooky or utterly unrealistic at first, but they've got a serious political machine that usually manages to come away with SOMETHING to show for it. If nothing else, they end up with more power they can invest later.