I've been reading about Mao Zedong and I heard about his Great Leap Forward. I read that it ended up splitting families apart and causing a massive economic crash. Why didn't Mao Zedong see this would happen.
Knowing why a dead person believes something or not is hard; but what we can tell is that Mao believed that the Great Leap Forward would work, either out of incompetence or arrogance, and he had managed to silence his critics and those that would have forseen the disaster.
In this sense he is far from alone in history; a most similar example would be Stalin and Lysenkoism. In both cases a nation blinded by revolutionary zeal chose to place their faith in ideology and pseudoscience, causing a massive famine.
The myriad reasons for the failure of the Great Leap Forward can fill books. Mao was economically incompetent but a master politician; he trusted pseudoscience and political will over his intellectual critics, whom he purged ruthlessly. The only voices he heard were those similarly blinded by revolutionary zeal; his critics were too fearful and powerless to question the decisions until the disaster could not be ignored. Decisions on production quotas were made from the top down, they were highly unrealistic, and criticising or failing to meet those quotas only resulted in retribution. This created a toxic echo chamber where peasants were worked to exhaustion and records were falsified to create the impression that the whole plan worked.
A good example of this happening: Mao believed that a key indicator of economic performance was the production of steel, and so he encouraged everyone to smelt steel literally from their backyards. Peasants tried to smelt everything they can find, like pots and pans, stripped forests and even burned furniture for fuel. The result was mostly economically marginal pig iron, at the cost of large-scale capital destruction (pots and furniture are useful, you see).
I think there were more direct political intention behind all those movements that Mao led than what people think what the benefit should be from them. I think it all served really well in that regard, at least at the start.
Similar things in real live, when one looks for funding, or support to run a project, the attention or interest of the audience is always primarily considered, the value or consequences is secondary, at least for those who want to be in charge.