growstuff
Much of the damage is caused by a cytokine storm, which is an over-reaction of the immune system. Scientists are still working on the exact mechanisms. What would appear to happen is that some people knock out the virus right at the start of infection. Vaccinations usually do this. However, in some cases, the infection continues and the body tries to rid itself of the virus by a massive over-reaction. There's a theory that there's a tiny piece of faulty DNA involved for some people. The virus attacks multiple organs, not just lungs, although most people who die suffer from respiratory failure. Blood clots stop oxygen from reaching vital organs, including the lungs.
Some people are at higher risk, but everybody is at some risk.
That is very interesting, @growstuff, and makes a lot of sense. I have an over-active immune system, which destroyed the insulin producing cells in my pancreas many years ago, and gave me a form of ME/CFS after a dose of radiotherapy, so it can do life-changing damage. I haven't had Covid yet, but my daughter had it and has suffered from Long Covid for many months; I wonder if she has inherited my over-enthusiastic immune system!