The Greeks?
Meditations is largely Marcus Aurelius soothing himself with logical arguments.
Im not doing it full justice but the passages read like “A whole is not less than its parts, Humans are intelligent, therefore the universe is intelligent, there for my situation is a logical plan from the universe, so I should be content.” Marcus was explaining why he needed to be the perfect elite Roman citizen, using nature to logically show why he needed to embody societally cherished traits like being logical, just, fair, but also being stern, powerful and strong. Over and over again.
Now at the time, they did consider it a hard science. They were trying to figure out secrets of the universe, the absolute correct ethics, and therapy (controlling your emotions) at the same time. Each tenet relied on eachother, you couldn’t have one with the other. Today we know the science was wrong and ethics are more complicated than they could’ve imagined, but the controlling emotions side remains. So I completely disagree that modern stoic bros are bastardizing it, it just is an flawed ideology that matches well with some of our modern western traits of a “masculine” man.
This is so false it deserves comment. For example, the SEP for Stoicism [1]. You'll notice that the first entire two sections are Physical Theory and Logic. Ethics comes later and it isn't until 4.3 (after Telos and Virtue) that you get to indifference. From the intro:
"Stoic philosophy was, from Zeno onwards, conceived of as comprising three parts: physics (phusikê), logic (logikê), and ethics (êthikê)."
I think you are over-indexing on one work by one Stoic. There is much, much more to actual Stoicism than "controlling your emotions".