The combination of having had many "opportunities" to experience the behavior characteristics when major hard-parts touchdown on an identical early-gen Ninja 250, over the course of the 120,000 miles of backroads riding - with the fact that the OP (Billy) acknowledges being a very new rider - pretty much answers that question.Can't really tell whether the rear was breaking loose due to loss of traction before the hard parts started touching down...the OP could chime in an tell us whether or not scraping of hard parts was a "normal" part of his cornering experiences or one in a million.
I can assure you that at a newer rider level, regularly experiencing hard-parts on one of these bikes scraping in corners would NOT be a recipe of something repeated very many times before ending up crashed-out, as occurred in the event associated with this thread. By the time noticeable (to a newer rider) first occurs, the leveraging of the rear tire is only milliseconds away. Catching and correcting that for an experienced rider is a crapshoot at best .... while the chances of doing so as a newer rider runs right up there at the lottery winning level!

Anyone questioning the hard-parts touchdown as the triggering moment .. please just go back and listen closely to the audio component in the posted video, and the timing in its arrival with the bike's swinging out and beginning the lowside crashing sequence. That's was the hard evidence for me in the post-crash diagnosis, in connection with my own personal experiences on that same bike.
Believe it, or not ....... that's up to you ...... as everyone's free to go with their own opinion; but giving correct "how to prevent" advice to the OP is the most important outcome from the thread .