Why it takes several days to enter inflammatory phase in COVID-19?

Why is it there such a clear separation of phases?

Why do people with mild symptoms go on to die? It is a great mystery.

Ciro Santilli's theory is that COVID is extremely effective at avoiding immune response. Then, in people where this is effective, things reach a point where there is so much virus, that the body notices and moves on to take a more drastic approach. This is compatible with the virus killing older people more, as they have weaker immunes systems. This is however incompatible with the fact that people don't seem to be contagious after the viral phase is over...