why did captain Silver hated squire Trelawney ?

Squire Trealwney is the figure in the book who financially underwrites and initiates the treasure hunt. Although he appears to be on top of things, he often makes mistakes and his hiring of Long John Silver and the mutineers tops the list of misjudgments and miscalculations which lead to the downfall of the journey. He is very naïve and trusting, and, thus, is constantly being duped. Silver sees Trealwney as part of the elite establishment. He does not respect hi naivety or his instincts.

Look the answer quite simple, a major reason was envy. Silver also hated Mr. Trelawney becuz the squire thought of John been a part of an elite establishment, which Silver despised .Silver had no respect for the squire's inocence. Silver did not like him due to his naiveness and thought of him been a bit unworthy.Silver thought of him been a bit greedy as he wanted to have the treasure even he knew his life was it danger. Plus he was not really in need of it.....

DMK