To quote Saul Alinksky’s Rules for Radicals, a book I really wish movement/community leaders and organizers would bother to read:
[A] single issue drastically limits your appeal, where multiple issues would draw in the many potential members essential to the building of a broad, mass-based organization. Each person has a hierarchy of desires or values; he may be sympathetic to your single issue but not concerned enough about that particular one to work and fight for it. Many issues mean many members.
Occupy’s failure wasn’t because of having too many issues. They never developed specific, immediate and realizable ones. What Occupy had was an amalgamation of problems, complaints and ideals. Because of that, they had no way of ever claiming a win as they never gave their opponents a way to give into any of their demands.
Of course there were a whole lot of other problems including tactic fatigue and not keeping the pressure on by switching up tactics, but that’s a longer discussion.
BLM at least has actionable issues. They come out when someone gets shot, at least one of their actionable issues is getting the police officer fired or prosecuted. They can claim a win when things go their way which keeps fuel on the fire until the next issue comes around for them to pounce on.
Edit: Oh I should note that the Tea Party (well FreedomWorks) actually followed Rules for Radicals - while demonizing Saul Alinksy and linking him to Obama (a tactic that fit right in with the Rules themselves).