Most traders who don't trade options assume options markets are someone else's problem. Fabio Ruggeri's data suggests that's been wrong for the past five years.
Pre-2020, options volume was dominated by institutional hedging. The effect on price action was real but manageable. After 2020, retail options participation exploded. The flows got large enough that market maker hedging became a primary driver of short-term price behavior in indices like SPX and in individual large-cap stocks.
When market makers are net short gamma, they buy as price rises and sell as it falls, which amplifies moves. When they're net long gamma, they do the opposite, suppressing moves and compressing volatility.
This regime switch happens at known price levels, and the data to identify them is publicly available.
Most price-based systems were built before this dynamic was this influential. The traders ignoring options flow are operating with a model of how price behaves that the market partly left behind after 2020.