yitayningwut: Rav Krausse from England proposed that chocolate should be HaEtz and asked many Gedolim. Numerous Teshuvos were written to justify the common custom to recite Shehakol. Some of the answers, such as cocoa being a minority ingredient of most chocolate, are irrelevant to peanut butter. Many of the replies appear forced.
I personally attempt to be machmir on myself to always make Shakol and HaEtz on other items before eating chocolate, but the consensus of all the Gedolim was that the primary Halacha is Shehakol, even though I’m not satisfied with any of the reasons.
The real reason seems to be, that the Shaarei Teshuva records the Beracha in chocolate as Shehakol. However, he was referring to a drink, not a bar or other solid. Drinks are intrinsically different, as Tosafos and the Rosh explain in the context of why we do not say Mezonos on beer. This is the answer also to orange juice. A liquid does not retain the original beracha, even when most are squeezed.