I haven't read any dives into the postmortem analysis yet, but based on nothing but the video of the explosion, it looks like a control system sequence failure. At one point you can see the grid fins deployed, and the vent plumes from the second stage tanks were at an angle to the vehicles axis, which means the whole stack was already moving a bit sideways. The commentary mentioned the turn-around maneuver, but its not clear if that was actually occurring when announced, or was just anticipated. If it was already in the turn around maneuver, it would make no sense to allow that command or grid fin deploy command until stage separation was confirmed. Also mentioned in the commentary was max Q, but again, not clear to me if it actually got that far, or was just mentioned by commentator.
I was in the car during the launch, and listened on youtube for about 2 minutes until the explosion. I was on my way to a welding facility, and ended up working with a welder who developed the welds used in the raptor engine nozzles. Spacex ended up purchasing a few welding machines for themselves (~$4M each) and continued their production in house.