For my case, it is quite simple -- people have different preferences and switching costs! I chose economics as a field of profession because I felt it explained human behavior much better than anything I'd come across in my life at the ripe old age of 21. Had I started my studies less than two decades ago, I would have invested more in physical sciences (especially hydrological saline exchange and improving soil quality through mycology, both fascinating problems some of my close friends study). This said, my data science company was founded two years ago to focus on impact problems in health, technology, and geopolitics, all of which are becoming more and more impacted by the effects of anthropogenic climate change in addition to just out and out pollution and bad policy effects.

But I think your first question is less why I personally studied computational economics and industrial organization, and more why economics exists when humanity may be facing a global extinction at worst and a loss of living standard at best. And the answer is: economics can be used to help with mitigation (and economists have been calling for effectual policy to address climate change for _decades_ through known effective policies like carbon markets, see subfields that research environmental economics and public economics).

Now, economics can also help understand why we see little meaningful action. Rational people (defined as being able to make comparisons between options presented to them, which simplifies analysis without much loss of generality to cases like bounded rationality) do not choose what is best for a collective (personal happiness/utility) nor what is best for them tomorrow (time inconsistency of preferences) when neither of those have meaningful impact to them today or in the near term. You see this all the time in the startup world and in the corporate world among VCs and executives who are only in things to accomplish short term goals. Self-organizing collective action is _hard_ to generate or maintain without enforcement of some kind.

To explain with a workhorse model regarding collective versus individual action, you can reference the stag hunt game: https://en.wikipedia.org/wiki/Stag_hunt. In short, while two individuals engaging for collective action will benefit more in total, there may be incentives to deviate from a collective strategy. People want more _now_, not 75 years from now (beyond the lifetime of the current living).

So TL;DR:

1. Preferences! Or, rather, subjective valuations of research topics by people can vary without applying presentism to near history

2. Because economics can explain failures in collective action, but it doesn't control or recommend against collective action goals. In fact, qualitative economic approaches to policy are often highly successful. So the gap on meaningful action is more related to political will and the incentive to deviate or adopt a policy that isn't Pareto improving.

In short, we pay people both for their time, purchasing of objects, and for use of their assets (without commenting how how fair or unfair their capital acquisition practice was to this point).