Separation is much closer to the launch pad in Texas, the booster barely makes it downrange at all before turning around. This being filmed from the Bahamas with this much lateral velocity, gotta be the Ship breaking up. Likely the FTS triggered after enough engines failed that it couldn't make orbit / planned trajectory.

I dont think so. I think it is the breakup, with a large mass visible. most of the material will continue on until it parabolically renters and burns up in a visible manner

No, if that was taken from the Bahamas, that's an explosion connected to the loss of the 2nd stage.

Staging happens closer to the Texas coast and I don't believe you'd have line of sight to it from the Bahamas.

I'd say it might be after the loss of the craft. It was losing engines for a while then lost telemetry. This would have been a bit later when it started tumbling in the atmosphere on re-entry. Hopefully we'll know for sure in a few days.

That's for sure not stage separation, that's an explosion from the FTS rupturing the ship tanks.

If it was the FTS wouldn't the flight control systems send a message back to the ground saying "things are going sideways here, FTS Activated"

Maybe it did, or is it public that it didn't? A possible sequence (very typical in rocket failures) is: fire, engine failure(s), loss of control, rupture due to aero forces or FTS activation, explosion due to propellant mixture. Not all of these have to happen, but it's a typical progression. Before the days of AFTS the FTS activation would be pretty delayed.

Eh I'm thinking more it was a reentry explosion from pressurized tanks. Engines had failed a while before then.

This is over the Bahamas. Re-entry was much further east, near Turks and Caicos Islands.

Also, if a pressurized tank is reentering, that means the FTS failed to detonate.

Nope. That's definitely an explosion (source: I'm in the rocket business). However it may not be an explosion of the whole stage. Probably of the engine section.

Nevermind. It was probably the FTS like other people pointed out.