I am thinking the theories are true because of the must larger negative repercussions of that action.
They are strengthening the regime (US intelligence services were aware of that before the attack and had informed the president), they are destabilizing all their oil producers, they are risking great economic cost..
It only makes sense if indeed they either extorted him, or if he is indeed demented / deranged.
Have you seen population pyramids for the west ?
There will be too few people.
Additionally I will argue that if you care about the environment and our planet, it is your duty to have children and educate them about all these things.
Regarding the doomerism, I will brush it off as internet caused (too much news/social media)
Nobody knows what is going to happen and where. For all we know things might go amazing. It doesn't look like it, sure.