So, something the article mentions is that SpaceX planned for the rocket to explode. That seems odd, why would they want that?

They don't want it to explode, but it is an expected outcome during initial testing like this. Starship is not like any other rocket ever made. It also has very little in common to the existing Falcon 9. Almost all of its design is new and has not been done by any other company. From the steel structure, to the full flow staged combustion rocket engine, an engine design never actually launched previously.

SpaceX operates using iterative design. They build the current design and find and fix issues as they complete it. Once complete they may not even be able to use the specific one they built due to changes in design, but the build teams get extremely valuable experience working with that iterative design and solving issues in the real world.

Most other companies instead spend decades and millions or billions of dollars designing and testing without actually building anything until they have a design they think is final. They then begin to build that model and inevitably discover issues that were never found during design, sometimes requiring large changes in design. See the entire SLS program and subsequent cost-overruns and delays.

In this particular case, it should also be pointed out that the rocket did not explode on the pad, it did lift off. The damage from the pad destruction may have actually been part of the Starship failure, not the Starship itself. The pad structure itself was part of the launch test as well, not just the rocket. The launch caused massive damage to the pad, which was expected and planned for. A water deluge system was planned, but not in place yet. They decided to launch as is to get real world data for what the actual damage to the pad would be. No data existed for what would happen to a launch pad with thrust this high at launch, and the deluge system may not have been enough as designed. No way to know without real world data because it was so far away from any previous tests anyone has ever done for launches. Even the Saturn V, the biggest rocket ever launched, had less than half the thrust at liftoff as the Starship Booster does. The Saturn V had 7.5 million pounds of thrust at launch versus Starship's 16.9 million pounds of thrust.

Very little about Starship has ever been done before. Almost everything related to the vehicle itself, the first stage booster, and the launch pad are entirely new research with very little theoretical research and development, and with almost no real world testing before. SpaceX is not following anyone here. Just like landing rockets for re-use,they are blazing an entirely new trail here no one has done before. And that means there will be failures along the way, they are 100% expected at this point.