We have been absolutely battered for decades.

People then quote “8 billion” an innocent or naive take. Consider the mathematical consequences of this. The more sperm there is - the greater the competition to reach the egg first. Less sperm overall = lower quality and more easily controllable humans are born.

Also - the quality of the sperm cells is declining along with the overall count.
These people know exactly what they're doing.
Full spectrum assault on humanity.

So what's caused this sharp decline? Wrong question. What's NOT causing it? is a better approach.