My cut on all this:
Some, but not all of this, is the result of sampling issues.
@DavidcCrowley had just re-entered the race when many of these polls were taken. Some were taken before
@TheOtherMandela dropped out, allowing Crowley to consolidate vote.
Also, more than $4 million was spent on TV on Crowley's behalf between 7/18 and yesterday. Not a trivial buy in a short period of time.
Finally, Hong, who did remarkably well, struggled with the scrutiny that comes with frontrunner status and, unwisely, went on a tour of national news shows for which she was ill-prepared to answer questions, like on her past positions in favor of abolishing police---and Thanksgiving!
Crowley's sprint to the finish line broke late and hard and went largely undetected by earlier polls.
I did see some private, non-campaign tracking in the final days that picked up sharp movement in Crowley's direction and that momentum obviously continued.