I think it is not just one thing.

Likely, true.

Whatever this new something is,

5G emits radiation. Wuhan, China was the first fully-5G city in the world. Northern Italy was next.

Seattle, Washington led the way in the USA.

Think about it.

it needs a weakened immune system

"Immune system" is probably not what we have been told, either.

We have a "health maintenence system," that is constantly trying to cleanse and heal, as needed. The more toxic we allow ourselves to be, the more health symptoms we experience, as our body tries to detox from more and more contaminants.

polluting of soil, air and water accomplishes,

Polluting of air and water is a problem. A real problem, unlike so-called "global warming."

As for soil, it is the mega-agricultural monocrops that destroy the soil, which destroys the environment and the food system.

But that can be reversed through regenerative farming. Look up Allan Savory online to see his amazing presentations of how he turned dry, barren land in Africa into a lush agricultural oasis.

explains why the high risk groups were worst affected.

These "high risk groups" are simply the people who are the most toxic from their lifestyle choices.

Not what they want to hear, but ... tough shit.

They'd rather take a pill than put down the fork for a minute.