They did, but no one cared. Their excuse was, if you want Trump out, vote/donate for the other guy or have armed rebellion to overthrow the government. Armed rebellion is not gonna happen since US police are absolutely brutal in cracking down on armed dissent. They even use military vehicles.Note that in the US, even at the height of BLM, nobody called for Trump to step down.
But the same should apply to china. Wanna overthrown Xi, then you gotta join the party, move up the ranks and displace him. Otherwise it's armed rebellion against the CCP, which is magnitudes harder now then in 1989, if not impossible.
With all the cameras and technological monitoring, I'm not surprised they protested at night as people used a vigil as an excuse to get together, because if it was planned, I don't think it could have gotten off the ground.
I sure hope the MSS got an ID on all of them and monitor their phone, browser history, bank accounts. China is not like Iran or Syria.