Is it possible the thing that regulates the thrust, over-thrusted? 108%?
My guess, as a sofa slug, life long launch watcher (with no engineering qualifications) — is that one of the nozzles fractured or separated thereby causing the engine to combust without containment (the brief bright flare) Shortly thereafter this caused fuel in the feed lines to detonate (the mid-air explosion) and after that the stack dropped onto the pad and couldn’t help but explode the remaining fuel.
108% is part of the planned liftoff. It’s a throttle setting, not a thrust measurement.