It looks to me like there was a problem with second stage separation and/or ignition. It appears that the first stage engines do not cut off prior to second stage ignition. With a a disposable booster rocket engine cut off is assured with propellants running out.
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"Don't disturb my circles." translation of Archimedes last words
I've watched a few views and I think it was in trouble early, long before it actually blew. I also see an initial smaller explosion that causes a rain of white debris several moments before the big POP. look at the plume from an earlier launch and how uniform it appears then look in the paragon from the latest flight that failednormal
in real speed you can watch this flame licking back and forth