If health is a gift from God, why is it correlated with naturalistic means?

If health is a gift from God given to those who pray for it, why is the health and longevity of a people directly linked to the quality of healthcare in that nation not their religion/lack of?

For example, Congo, one of the largest Christian nations, with 95% of its inhabitants identified as believers, has an average life expectancy of 49. (1, 2)

On the other hand, Northern Europe, which includes large populations of atheists (estimated upwards of 60% in some Scandinavian nations) has an average life expectancy of 81. (2, 3)

If health comes from prayer, why do the third world faithful die young, while the faithless with access to modern medicine live longer?

Why did God stop intervening in order to save the lives of the innocent?

In the Old Testament we see examples where God prevents the sun from moving, fire/hail coming from the sky to kill enemies, and whole attacking armies are instantly blinded to save praying people. For example, when Judea was under threat by the Assyrians, and Hezekiah prayed, the text says an angel flew over the Assyrian army and killed 185,000 soldiers instantly. (2 Kings 19)

Why has God stopped doing that? Why not send an angel to instantly kill all of the Nazi soldiers who were rounding up the Jews or attacking Europe? (Surely millions were praying just as eagerly as Hezekiah) Why not instantly blind all the rapists who are currently attacking children?

These are all the kinds of things that were reported in the past, so why have they stopped now?