When nothing in a system works, it's default diverging.

When you land code, even if it incrementally breaks an extra thing, you don't notice or bother fixing it.

When a system is working and load-bearing, then when your change breaks something, you fix it.

But all it takes is a few broken windows in a product that's not heavily used to get to default-diverging.

It requires constant effort to keep it working until real load-bearing use starts compounding, at which point it has ignited and is default-converging.