From my understanding was from reports I've read. Separation was abandoned due too the explosion after take off of one of the hydraulic controllers on the side of the Booster, which caused the Super Heavy vehicle to be unable to gimble it's center engines. I believe had it not lost that, the rocket could have gotten high enough to separate. From what I understood was, once it became apparent they lost control of the booster. They abandoned effort to separate stage 2 aka the Starship.
However, it was outright stupid thing to do gamble launch site on withstanding the thrust of the engines blasting down on it. I always though that was bone head move by Musk because he was in a rush to launch and test. Now unfortunately, the company is paying for it. Hopefully, they learned enough to fix the other tower in Florida or make new site with proper flame diverter. This cooling plate Musk wants to use is likely not too work, but I'm no engineer or scientist.