While the telemetry was still going, you could see Ship engines going out one by one. Earlier when there was video there was what looked like flames visible inside one of the flap hinges, definitely shouldn't be there on ascent. Presumably something failed internally and caused the Ship to shut down before reaching target trajectory, at which point either FTS or the failure itself caused it to blow up, as seen on the Insta reel.

On the NSF youtube channel they pointed out that at some point the methane indicator started decreasing much faster than the LOX indicator, which points to some sort of leak. It would explain why the engines started to shut down.