How does a troll "spread" stuff ? FB does the spreading with the algorithm right? Am I missing something? What I see on FB is people I know share/like dubious

How does a troll "spread" stuff ? FB does the spreading with the algorithm right? Am I missing something? What I see on FB is people I know share/like dubious shit like "Japan made microwaves oven illegal" , the original "troll" did not put this one my home page, people did not directly sent me that shit, FB decided "let me show this guy that the other guy seen and like this shit article on some other guy page", FB done all the spreading and even if FB had my and all my friends IDs it would not have stopped this stupid shit appeared on my wall (everyone has their real names and birth place, education, family relations setup in FB)