The more cynical reading is that this is a purely a political move for the mayor-elect. Perhaps Chiara DeBlasio is just a relatively normal 19-year-old woman who experimented with marijuana and alcohol in college, but whose typically undergrad exploits might reflect poorly on her father — especially considering that Bill DeBlasio, far more than any other candidate in the mayoral race, put his family front and center during his run: His son, Dante, appeared in an emotional video about the threat of stop-and-frisk police tactics, and his wife, Chirlane McCray, played a prominent role in his campaign and has been frequently cast as his "co-mayor."
As to why the video, which The New York Times described as "carefully crafted," appeared on Christmas Eve, DeBlasio's team is reportedly mum. (Certainly not to bury it; the slow news days around Christmas ensured it even more publicity.) The Times also suggested that Chiara's drug use was "long a subject of speculation in the New York political world," and that the family wished to tackle the issue without the cloud of the campaign and on their own terms.
It's understandable if Bill DeBlasio and his team wanted to put everything on the table before he takes office next week, effectively defanging any opponents who might want to damage him in the future. Whether Chiara was complicit, or merely thrust in the spotlight to preemptively disarm what might not have amounted to a scandal in the first place, we probably won't know any time soon.
No matter the impetus, however, the value of her message remains the same. (NYT)