A true sentiment is told by the actual prices. Currently SPX is at new high that reflects a true bullish sentiment. Its the votes from traders and MMs.
The actual prices represent completed transactions of the moment the result of open market price discovery.
Most trades these days originate from computer models that have unsentimental constructs. As far as I know no one is polling computers.
Individual traders are more intuitive and impulsive so their opinions are closer to what the public may think and their opinions end up in sentiment polls.
The various sentiment measurements may or may not agree with price at any time but the deviation of sentiment from the price is very valuable information because it reveals people's expectations and suggests to what degree people may be invested at that phase of the market or are their expectations reasonable or not.
Often the prices just oscillate but at times there is an element of surprise that triggers a breakout move. One of the few edges in trading is if one can figure out how to get on a move near inception, at the beginning of reversals.
More often then not in these situations sentiment was lopsided and created conditions for the element of surprise.
The person who read sentiment correctly (and using technical tools like divergence and volume analysis etc) may have profited from the move.
Regards,
f&d