Why everyone started to think internal intention is the only good thing

The modern split between "inner" and "outer" goodness stems from the loss of natural teleology — once you deny that things in the world have inherent purposes, goodness can no longer reside in actions themselves and gets trapped entirely in human intention, producing the familiar but incoherent idea that being "good on the inside" is what really matters. This shift generated both utilitarianism (goodness as subjective feeling) and deontology (goodness as obedience to moral law), and stands behind the Tanya vs. Nefesh HaChaim dispute, the modern reinterpretation of kavana as a mental state rather than a description of what you're actually doing, and the strange claim that Torah lishma is about your headspace rather than your learning. Purim embodies the corrective: chitzoniyus IS pnimiyus — happiness is not a feeling but a fact, realized through concrete action like matanos l'evyonim, not through interior emotional states.