From some of the research I've done, the virus has the potential to attack our immune systems making them not work as well. So this way any illness is more likely to kill us.

Because the current virus is weak sauce, and they don't want to die from some strong unpredictable virus.

Think about it.

Panic! A bunch of people jump on a "cure" that actually weakens them. New virus! (Same or similar to old virus) Rich and people with half a brain do not get the shot. People who got the shot way more likely to die.

Instant population control. Thin the herd.