Is it really the crowd becoming intelligent or stupid, or just that we are agreeing or disagreeing with the crowd and conflating that with the intelligence of the crowd?

As a quick test to try and determine this: try to think of occasions where you thought of a crowd as intelligent: did you agree or disagree with the crowd? Now try to think of occasions where you thought of a crowd as stupid: did you agree or disagree with the crowd?

If these questions are highly correlated, then you may not be measuring the intelligence of the crowd as much as you think you are. That we think of crowds in these two extremes is also a hint.