Why Panjandrum ranked below the K-class submarines

Why was Panjandrum ranked worse than the K-class submarines?

The list counts down toward the worst invention, so the fifth-worst K class ranks above Panjandrum, whose rocket-driven explosive wheel threatened its own launch crew.

The ordering counts down toward the worst invention, making the K class the least bad of the five selections. Panjandrum was meant to carry about a ton of explosives through beach defenses and detonate against a wall. Its rocket-driven cartwheel was judged as likely to kill the people launching it as the intended enemy.