I am flying from SFO -> DEN in a few days and I see that Denver wait time is 4 minutes and, as is well known, SFO does not use TSA or federal security staff.

Denver does, however, so I wonder why there is no wait at DEN and hundreds of minutes at Houston/Atlanta/JFK ?

I’m a frequent flier and flown into all of the above, the ones with TSA issues have been perpetually mismanaged under the best conditions, it’s not even remotely surprising that they are having issues under pressure.