Why can I confidently write that police repression was the main factor ending Occupy? Look at the chronology of events in the Occupy wiki page. On Sep 17 2011, the encampment at Zucotti Park starts. There's steady growth through the end of October, with global protests on Oct 15, thousands of Occupations by the end of October. October 25, Ogawa Park in Oakland is raided. Nov 2, protestors close down the Port of Oakland. November 14, Zucotti Park forcibly cleared, with other clearances following quickly. Through November and December almost all of the major occupations were ended by police action. That is not a narrative of decline. Between mid-September and mid-November there wasn't even time for decline. It's a growing movement that was ended. Occupy continued after the encampments were gone, but never again managed to do anything that gained major public attention.
The major spikes in media coverage coincided with acts of police violence, of course. Occupy might not have taken off as much as it did without the pictures of Anthony Bologna pepper-spraying protestors on Sep. 24. Then there was Scott Olsen on Oct. 25. On Nov. 18, John Pike pepper spraying students at UC Davis.
But these were cases in which police attacked identifiable individuals. What support for Occupy would have really meant would be public indignation at the police raids that closed the encampments. After all, the U.S. Constitution supposedly guarantees the right of people to gather in public and protest. I'm sure that any number of constitutional lawyers could tell you how this right is limited and does not cover cases in which people want to actually use it, but people who are not so well-trained still have a general idea that it exists. Occupy, outside of Oakland -- Oakland was a special case that I'm not going to be able to do justice to -- was quite careful to stay away from anything resembling violence. One might think that people would support the right to peacefully protest even if they didn't agree with Occupy. Ideally, the raids that closed the encampments might have been the acts of repression that pulled in public sympathy for the next stage of growth.
That didn't happen. I don't think that anyone really expected it to happen, although I'm sure that the people telling the police to move in were concerned about it or they would have sent them in sooner. In part, it's just how America is -- it's a country that, as Ta-Nehisi Coates describes, was built on internal oppression, and all of its vaunted freedoms have always been illusory for people who go against the elites. This has never been a country in which ideas like freedom to protest were really a concern of the people as a whole, or the political class as a whole, instead of being particularly left concerns. But in part, it didn't happen because "the 99%" really didn't support Occupy.
Who was an Occupier? The archetypal early occupier was a recently graduated college student without a job. It was pretty much impossible to stay involved in Occupy if you did have a 9-5 job; it took too much of a time commitment. This, again, was not a choice that Occupy organizers made -- Occupy appeared as the winner of a pseudo-evolutionary process, and if there were other initiatives that were suitable for people who had less time, they didn't take off. And the occupiers typically had resources of some kind to fall back on -- if you don't have a job and don't see any immediate prospect of one, it's a really risky move to decide that you're going to gamble your existence on the continuation of a protest camp that feeds and houses you. Most people in Occupy implicitly had somewhere else to go back to. (I'm going to consider the homeless part of Occupy later).
By the idiosyncratic American definition in which an educated but poor person is "middle class", Occupy was middle class. It was not, culturally, working class. In addition, it always was a left-of-center movement -- there were never significant numbers of disaffected centrists or conservatives that I saw. Therefore, it was immediately opposed by the 1/3 or so of the American public that is engaged by tribal rightwing politics and hates anything on the left. Those people always actively support what they see as hippie-bashing. And, again outside Oakland, I never saw significant nonunionized working class support for it. There were plenty of centrists and moderate leftists who just didn't get Occupy and who were relieved not to be embarrassed by it any more. In addition, Occupy was primarily white. So when the time came for a swell of public support, it wasn't there. The people who supported Occupy were already supporters of Occupy, and the political class won their bet that repression would be effective.
ETA: Duncan Black:
It should go without saying (but it doesn't) that hostility to nonviolent public protests is hostility to democracy, hostility to the nobler parts of our history, hostility to our constitution and the right of free association, and basic contempt for the idea that the proles should have any meaningful way to express their grievances.
But only people on the left believe this.