I can understand why Founders worried about uneducated popular sentiment driving a democracy to foolish decisions might set up a bicameral structure in which it's harder to pass legislation. That's the cooling-saucer idea of the Senate (though as far as I can tell, the cooling saucer metaphor is based on an apocryphal story). Under such conditions, it makes sense to make the upper house have six-year terms so it doesn't suddenly turn over. If you're going overboard, you might also have other elites at the state level choose the Senators, as was originally done.
But if you assume a world of sudden and surprising challenges which technocrats can solve, but which the people are generally confused about, creating barriers to passing legislation ends up making popular sentiment win at the expense of the technocrats. Rather than having the barriers to passing legislation keep uneducated popular sentiment in check, it keeps technocrats from implementing any of their solutions. For example, you might have a financial crisis or a climate crisis, and the solutions are kind of funny-looking, but they'll work with minimal pain. In a unicameral system existing policymakers could just push them through, but with bicameralism it's easier for them to get stuck, which popular sentiment supports.
I remember Yglesias and Bernstein going on a while ago about how the Constitution is actually structured to protect a bunch of interest groups at the expense of technocratic policy proposals. That's certainly going on here. I guess what I find interesting is that if you're in a rapidly changing world where new challenges come at you from every direction, rather than a steady and stable world, political structures designed to keep popular sentiment from exerting too much force actually help that sentiment attain its ends.