I understand what is ecosystem inertia; it is exist...but as I know nobody suggested the concept of ecosystem inertia, which may be an explaining tool.....

I think there are many examples of this. For instance, there are regions in northern Canada where shrub forests developed during the Medieval Warm Period and survived through to modern times; these forests were stable as long as they were undisturbed. Disturbance (for example by fire) resulted in reversion to tundra. I am not sure if this more conceptually analogous to the physics concept of inertia (resistance to a change in state) or more to the chemistry concept of metastable states.

It must refer to that every natural ecosystem, will try to stay healthy, even when some factors could impact it.