How has Silver planted a seed of doubt among the crew members who have decided to rebel against Captain Smollett?

Insight into how Long John Silver organized the mutiny against Captain Smollett is provided in chapter 11.
Jim Hawkins crawls into an apple barrel to get apples and overhears Silver talking to members of the crew. Silver tells the men that he was once Captain Flint's quartermaster and that he is working to recruit other men who had been on Flint's crew to rebel against Captain Smollett. To convince the men to mutiny, Silver tells them that he plans on murdering Smollett and men loyal to him once the treasure is found. Then Silver plans to divide the treasure between himself and the men who helped in the rebellion.
In terms of why the men want to rebel (beyond the promise of treasure), they don't have a significant reason for being discontented. The crew lacks discipline and Captain Smollett is strict and serious, while Long John Silver is much more likable. Of course, Silver is revealed to be a cunning and duplicitous murderer, but by all appearances he could be seen as a more favorable captain.