An alternative explanation is that they are trying to push the design of Starship to its limits.

All the failures have happened with Starship v2, where the ambition is to put 100 tons to Low Earth Orbit. The previous design, Starship v1, was only (theoretically) capable of lifting 80 tons.

20 tons is a huge difference, basically what Falcon 9 can lift when launched in expendable mode.