I think you've accurately identified a real tension here, and this connects with a fundamental critique of EA as a movement, which is that it is too often focused on measurable outcomes rather than systemic change. I tend to agree that this critique has teeth and applies to the way EA is often practiced.

I do want to highlight that Global Health work is not inherently a temporary fix. Global Health work frequently can (and should) focus on improving existing health systems, not just having a temporary impact. By addressing the root cause, you can make a more permanent difference (and be more cost-effective while you're at it)

So why are more EAs focused on Global Health instead of Global Development relative to your expectations? In my opinion, two major reasons are

1. Some people are likely overly focused on measurable outcomes over systemic change.
2. Some types of Global Health work is more systemic than you give it credit for.

I was inspired by my ties with the EA movement to go do a degree in public health, and while I did not specialize in global health, I did take several classes in global health while getting my master's. One thing I want to say is that the division between global development and global health is much, much stronger within EA than it is in more mainstream global health. At least as taught at the UW, the intro global health class is just as much about international monetary policy and its effects, as it is about implementing specific scalable health interventions. And, income is one of the three most important social determinants of health globally (along with nutrition and education). This division is stronger in EA imo because it is easy to sell donors in our community on very specific, measurable, high-impact interventions, rather than engage with the politics that end up inherent in the development space. (And that's not even necessarily a bad thing, if it moves money counterfactually). But, global health as viewed by EAs is not the whole of global health--and (controversial!) I think it's good that we haven't upended the entire global health space to the relatively narrow set of GiveWell-approved interventions.

talk to @David Nas and @Karthik Tadepalli ha. There's increasing work within EA on development directly There are big questions around how tractable it is, how much EA influence can actually move the needle with huge money injectors active like the imf and world back, to and market forces as well. 

And yeah like @Evan LaForge said to some extent development needs good health and education to happen (a bit of chicken and egg)