It is possible many or most of the reported screen cracks are due entirely to thermal changes. The M1 MacBook displays are made of glass. Glass is a poor thermal conductor and rapid changes in temperature will create stress fractures in the glass that will eventually crack. When heated, thin glass begins to crack.

Let's say, for argument's sake, the OP has their desk in front of a window. At night, temperatures go down, and in the morning, sunlight provided enough thermal change fast enough to cause a small crack, which expanded with stress. I'm not saying that is what happened, just that thermal stress can explain a lot.

Voices can already be heard that Apple's product can't even handle sunlight. But it isn't sunlight, it is the delta-T over delta-t the change in temperature over time. Taking a device in thermal equilibrium of an air conditioned environment outside into a hot car will crack the glass with no impact event. Happened to me. I was holding an iPad in my hands in front of me, and I saw the glass crack, and I knew immediately what I did wrong. The change in temperature was too extreme and too fast.