I think the difference between your examples is timescale.
People are generally good at responding to acute, existential threats. We don't seem nearly as good at managing abstract ones that occur over long timescales. I just don't think we're wired to think about risk accurately in that way and, let's face it, most decision are made at an emotional, visceral level.
I would also say that defense contractors are some of the largest donors to the political class (not sure how they rank in media spending) and politicians have an incentive to solve near term crises and ignore long term crises. I would not say this is purely down to human “wiring” but the real world political structures we have today (which in theory can be changed).
I should also note that, regardless of how one feels about him, two things about Bernie Sanders are that he didn’t accept any SuperPAC donations and he was very willing to put effort in to eliminating student debt and alleviating climate change. So such platforms are not unheard of.
I think this is part of the issue, but we may disagree about the magnitude. As a counterpoint, "Retirees" are the second largest political donors behind the financial system and yet the retirement system is perpetually in peril.
My comment about our "wiring" is about how we are bad at estimating risks. We likely evolved to think causally rather than statistically and, when coupled with highly emotional risks, it tends to skew the accuracy of risk assessments. Climate change is not as emotionally charged as, say, terrorist attacks so it will tend to get lower priority in an individual's mind.
People are generally good at responding to acute, existential threats. We don't seem nearly as good at managing abstract ones that occur over long timescales. I just don't think we're wired to think about risk accurately in that way and, let's face it, most decision are made at an emotional, visceral level.