The booster separated & did the flip but not all engines restarted and those that did cut off. The flip probably screwed up the fuel flow and may have damaged the engines. The auto disconnect from the LOX feed on the side of the booster also leaked.
The second stage was nominal for a couple of minutes but a plume started & the LOX volume started to fall more quickly than normal, which would indicate a leak somewhere.
It will take several iterations to get right. I believe the second stage was the largest single vessel to ever reach space.
It was amazing reading some of the comments on YouTube how this was just another failure because both stages blew. They were extolling the virtues of Artemis, how it worked perfectly the first time...after how many years? At half the thrust of Starship, and not designed to be reusable. Some people just don’t get it.