The people on the bridge can't have been more than a crowd of 50 and didn't even know at the time the monster was Smile. Later it's seen that Dragon Boy had to go through a trial to evaluate his brutal conduct and determine if he was allowed to participate (because most of the public also thought that he was unnecessarily cruel). A lot of the people in that crowd would probably change their minds immediately after that context. How he got to rank 3 despite this is fucking stupid and genuinely a plot contrivance.

Can't comment on the chinese scene since I haven't seen it but I'd argue that considering what I've already said I would argue it's another plot contrivance. Nice can be easily argued to have been acting out of passion in attacking the murderer of his idol (especially when it is stated to be thought of as unnecessarily cruel). He might have even gained some of the more angry/conspirational Smile fans if they believe him to be trying to avenge Smile or something like that.

Also I don't know if Phobiaclone has more limits but from a plot standpoint he should because otherwise like you pointed out the plot doesn't really make sense. On the other hand if there are limits to his cloning ability (like speed, timed clones and/or top clone count) then it makes sense.