Golan didn't choose the hive mind over the Seldon plan. He chose the hive mind because in the short term (the 2nd 500 years of Seldon's plan) it would maintain the status quo. Also, Pshychoshistory doesn't say no one individual can affect the future, it is that it can't predict the actions of individuals. That is why the Second Foundation exists, to correct for individuals and to always keep an eye out for a better solution. That is one reason why they orchestrated the crisis so that they were left with only a single path forward. And if you pay attention to the stories, very often an individual made the crucial decision that solved the crisis.