Looks like a Frecciarossa 1000 derailed in 2020 but it was due to a manufacturer defect in a track switch replaced the night before.

The defect was not caught by the manufacturer or the system operator. It was due to two crossed wires in an assembly.

I know a lot more engineering goes into these trains due to the higher stakes. Japan’s high speed rail hasn’t had a fatal accident in 60 years. I’m wondering what the cause of this will turn out to be.

Actually the defect was detected by the operators, who installed it that night. They disabled the switch, but apparently this didn't reach the day shift.

Japan's shinkansen system has never had a fatal accident, except for one incident in 1995 where someone got killed at a station because he was caught in a door as the train departed the station (https://en.wikipedia.org/wiki/Mishima_Station_incident). No one has ever died in a derailing, crash, etc.