It would not be debris produced by a decoupling that loses speed, with decrease their centripetal force progressively, so therefore progressively they fall to the earth, deorbit.

It would be a cluster of successive collisions in a short period of time. With each collision, each destroyed satellite would produce hundreds of thousands of microfragments at increased speeds, with would make them reach different orbits.

The microfragments at lower heights of LEO would decrease their speed due the atmosphere within months to a few years, and the ones at higher heights of LEO from decades to centuries, but this ones, at time they loses such speed they would decrease the height of their orbits and sweep across their new orbiting area (like a net/mesh), their kinetic energy would keep being able to destroy or damage what they cross.

If it were done it would be like a planned Kessler Syndrome event, and LEO is currently saturated with satellites.