In all honesty, it was probablysupposed to explode. Elon himself mentioned that the Mk1 probably wouldn’t fly, so this was probably just a test to see what the main tanks were rated to/what are the primary failure points. Hopefully the tanks held up far past where they thought they would!
She’s a robot. She’s fine.
Unless you’re Jamie and Adam, you typically don’t make things explode on purpose while testing.