None of them, to my knowledge, opposed it. They all could be supportive even if they don’t attend. Just because you support a cause doesn’t necessarily mean you can physically come, as you might have other responsibilities at the time that you feel take precedence. Such as Limud HaTorah, for example.
Otherwise, gedolei yisroel such as Rav Aharon felt it so important that not only do they support it morally they felt they had to close their Gemorah and actually come to make a statement. Not every godol necessarily agrees how to treat the same causes they support. Or the other Gedolim could easily have determined between themselves that Rav Aharon, could represent them all as he’s the senior godol on the Moetzes Gedolei HaTorah and Rosh Yeshiva in America.
And if you do find a godol or two who is officially on the record as having opposed the event? (I’m not sure any such exist, but maybe there’s a couple out there.) So what. Gedolim always have differences of opinion between themselves. Even when they might all oppose Zionism, they might have different approaches on how to fight it. Openly or quietly. Loudly or more tamed. Publicly or privately. Etc.
But in this case while there are scores and scores of Gedolim who officially and on the record supported the actual protest, I don’t know of even a single one on the record as opposing it. (And I’m not referencing those that only issued a letter saying that a previous letter in their name was a forgery. That doesn’t indicate one way or another if they support or oppose the event. Nor does it indicate the forgery itself wasn’t made by lay opponents of the event to make supporters look bad when they “discovered” the forgery.) If you know any on the record as opposing it, share with us that official statement of theirs. But that doesn’t change anything I wrote.