I've seen it written that some...if not many...people who entered government buildings did so in a calm,orderly fashion...almost as if if they were entering on an ordinary day as many tourists routinely do.
To the extent that that might be true it seems that they had no reason to believe they were trespassing.
Right -- and if a defendant can show that they were "waved in", or otherwise reasonably believed that, as protesters, they were being permitted inside just as had been leftist protesters against Kavanaugh, etc., they may have a valid defense to a charge of trespassing.
That defense obviously won't be available to anyone who pushed against police, broke a window, etc.. Nor should it be.