I'm stuck on a few challenges. It seems that when I invest more AP in upgrades I'm just losing faster. For example on United States I lost after ~7k days before and after improving Army Camp Discount 0% -> 26% I lost after ~300 days. It's a bit counterintuitive.

Edited 1/19/2021 16:01:25

Fizzer changed the difficulty of the challenges last update, so that is why you now lose faster while still having better advancements.

I'm losing faster compared to the same update though. I checked before and after buying.

I noticed it while trying to beat the first challenge, quite some time ago. The opponent ends up conquering my army camp, and beating me. After upgrading army camp income, I lost faster - autocapture used the increased income to capture an extra neutral territory, had less armies on hand when the opponent started tearing through my lands, got my army camp faster and game ended faster.
The particularities of the map have a great influence on how the challenge plays out.

That makes sense. The upgrades can change the timing then causing the auto-capture to make suboptimal choices. Still funny how much of a difference it makes.