Rentech trades on extremely reliable (but constantly evolving) price movement patterns and levers them up to the hilt in order to generate their returns. This is one reason why they are capacity constrained and can't just compound their returns. When the coronavirus first knocked US markets out of orbit, because of this leverage, the medallion fund was actually close to losing all of their money due to many previously established patterns evaporating too quickly for their algorithms to adjust. I have heard this from someone with first hand familiarity with ren tech. As others have mentioned, they also understood at a very early stage the importance of solid data ingestion and infrastructure. They vacuum up anything that could plausibly be related to price movements.