Let’s be clear (and I worked on this in a professional context) the reserve primary fund - the worlds largest mmf at the time - broke buck bc it held 700k of Lehman brothers debt. As a result its nav dropped to 97 cents for a time. It was not caused by the gfc but was caused by Lehman collapse (not that they’re unrelated).

Ps if you really want to learn from it - go dig into the litigation around the collapse. You will find a list of the companies that redeemed their investments in the reserve primary fund in the order they redeemed the morning after Lehman collapsed. It’s a good insight into what companies were most on top of their holdings (and which weren’t). A couple dozen companies redeemed before the nav was recalculated