[showerst]

I generally agree but one of your examples is in fact a counter-example -- the president and particular congress people tend to matter, as lawmaking is rarely the average of voter preferences. Does a median replacement president to Obama pass healthcare? Does a median LBJ manage to wheel and deal the Civil Rights Act? A Trump that just wanted to pass agendas instead of infighting would've done 5x more for republican priorities.

Certainly those people worked with a groundswell, but it took their extreme individual interests (or lack thereof) to determine those big outcomes.

I think this is generally true across congress too -- stuff that just happens to have a powerful champion goes far, other equally popular issues languish. My wife works in hospice policy and the selection of members who just happen to have had a good (or bad!) experience with a family member in hospice really changes which bills happen.