One aspect of the story of Dune that the movies don't make super clear is that, before Paul, the Fremen already had a central leader figure in Liet Kynes. In the book, Kynes has a generations-long plan to gather enough water to transform the environment of Dune (this is why the Fremen have those big pools, they never get super clear about that), then retake the planet for the Fremen and create paradise. Paul showing up and then leaning into the whole Lisan al-Gaib bit pretty much directly gets Kynes killed, creating a power vacuum into which he assumes himself with the aid of his previously-unheard-of levels of white privilege. While Kynes was an ecologist, however, Paul comes from a family of colonial military aristocrats. All Paul can offer the Fremen is all he understands: revenge. Bloody revenge for everything they've endured in centuries of oppression by the Imperium, temporarily in line with the revenge he craves for the Imperium's attempts to control him and his family, and spiritually in line with the resentment built up all across this socially stagnant feudal space empire.