Plans take time to adjust; I imagine a big part of the impact was companies realizing that they need to buy/rent much less expensive GPU compute to realize the plans they've already committed to for the next couple years. Being able to spend less to get the same results is an immediate win; expanding the plan to make use of suddenly available surplus money/compute takes some time.

And then part of the impact was just "woah, if some noname team from China can casually leapfrog major western players on a tiny budget and kill one of their moats in the same move, what other surprises like this are possible?". The event definitely invalidated a lot of assumptions investors had about what is or isn't possible near-term; the stock market reacted to suddenly increased uncertainty.