It seems that a faulty immune system is the cause in MS, and inflammation is the symptom... can you clarify your example?

Sure, the immune system is at fault, but it’s the inflammation that causes the damage. Since we don’t have great tools to tweak the immune system, if we prevent inflammation, we can stop the disease.

It seems illogical to attempt to redefine inflammation from a symptom to a cause because of the inability to cure the known cause.

Suppressing inflammation is still temporary relief, not a cure for the root cause.