They have data and probable causes, but nobody will tell until forensic studies take place, which seems a good decission. No need to spread speculations.

A cold start from zero generation took 6 to 10 h. No casualties, hospitals and crtitical infrastructure kept working all day.

Whatever the cause, this has been a great test of the emergency protocols.

What? Every single major power outage on this list https://en.wikipedia.org/wiki/List_of_major_power_outages has taken between a day to a week to diagnose. You can read about the list of detailed theories if you click through to any of them, here's an example: https://en.wikipedia.org/wiki/2020_Sri_Lankan_blackouts

Even your minor power outages take 30 minutes to an hour for your local power company to determine what failed.

its pretty normal not to know immediately when something with this many variables stumbles. it may take a bit, but they'll figure it out.