What was the secret of Pinchus's greatness? How did he become whom he became? How did he accomplish what nobody else had done?
Very simple: Pinchus followed the Chovos haLevavos (see Shaar Yichud haMaaseh) that says that a true servant of Hashem could not care less what people think! We are worshippers of Hashem, and not of people, no matter how great/distinguished/amazing they may be. How much potential greatness is lost due to unhealthy fear of ma yomru habrios, "what will people say?" A person needs a private rebbi who he feels comfortable with and respects, and who will guide him in actualizing his private portion in Torah in the way that makes him a bigger, better, happier, healthier person with a healthier connection to Hashem—and that's it! Without a private rebbi, a person can live a life of making the "street" (der gahs in Yiddish) his "rebbi," with copycatting and stifling, without actually ever fully recognizing his true personal potential, which is to take over the whole entire world, each person in his own way!
Pinchus was a novardekor (just joking, or maybe not so much...), and put all chesbonos and "calculations" on the side when it came to doing for Hashem! (And Hashem payed him back!)
