I've figured out their plan, this time, I, Cave Johnson, have done it!
Think about it. What happens with every false flag, end of the world prediction, and martial law prediction? We bring in our tomato plants, depriving them of precious sunlight. The Solar Doom predictions are just proving it. In the end, as it turns out... they aren't depopulating humans. THEY ARE AFTER OUR TOMATO PLANTS! Attack of the Tomato Killers. Damn you, PTB... well played.