Mobs do have leaders, who make speeches complaining about what is wrong, and what they want instead of the legal government. Sometimes mods succeed in taking over the whole country (Russian revolution), sometimes they fail because the government succeeds in using force to stop them. The British decision to ban the trade of slaves (William Wilberforce) was fiercely resisted by the people who made money out of the trade. Slave trade mobs attacked the homes of people known to support abolition.