You seem to have the key word, Could.
We see a lot of they moves come from the Housing Bubble Crash.
S&P's worst week in the period down -18.2% the week of 10/6/08 after its fifth worst week down -9.4% the week of 9/29/08. There were signs but you might have been out for longer than just two week. When would you have gotten back in for the 10/27/08 10.5%, 11/24/08 12%, 12/29/08 6.8%, 3/9/09 10.7%, 3/23/09 6.2%? It seems the the up weeks were clumping just as much as the down weeks.
I don't remember a single bear trader/promoter who flip 180 in mid-october 2008 to become a raging bull but that was the time to do it. Other than P/E, momentum factors, & other price or market driven metrics, no new info or data ever arrives quickly enough to change forecasts from week to week. Sales data, market trends, GDP, employment, trade etc. are all derived from data collection that can be weeks & months old & are frequently revises over then next months.
The base state of the stock market is everything is neutral its that it will grow. It grows because we have still have population growth (in the US & the world) & we still are getting productivity increases which expands the economy. To get a gain from jumping in & out your down accuracy must be very good because even missing a neutral week will be a cost. For most, they miss some good weeks & plenty of neutral ones to avoid the worst ones & then wait longer & miss plenty of the rebound hot week. The ones who can actually do it is a tiny percent of those who think they can.
How would you have avoided the third worst week? 9/10/01 down 11.05%? I did. I had a mix up in a reallocation. I sold on 9/10 & could not buy the new securities until the markets finally re-opend. I can't call blind luck as skill but many do.