One reason, it seems to me, is that the Occupy protesters were purposely — even proudly — rudderless, eschewing leadership in favor of broad, and thus vague, consensus. It’s hard to get anything done without leaders. A second is that while they had plenty of grievances, aimed mainly at the “oppressive” power of corporations, the Occupy protesters never got beyond their own slogans.
But the main reason is that, ultimately, Occupy Wall Street simply would not engage with the larger world. Believing that both politicians and corporations were corrupt, it declined to dirty its hands by talking to anyone in power. The takeover of the park — especially as the police threatened to force the protesters out — became an end in itself rather than the means to something larger. Occupy was an insular movement, whose members spoke mainly to each other.
The Tea Party did just the opposite. It, too, believed that politicians were venal, but rather than turning away from politics, its adherents worked to elect politicians who believed in the same things they did.