Nobody knows what triggered the selloff, it's a global market with millions of actors doing actions based on numerous sources of information. More than that we come off a peak of hitting SPY500 ~$600 and NASDAQ100 at $20.5k which are all time highs and it's very normal to retrace a bit after - but even that doesn't mean much.
Whenever someone tells you the reason for a stock market move, all they're telling you is what they believe did it, but they have no clue, other than specific critical situations as like, after 9/11 attacks. For company specific "this is why" it's much easier, but even then many times it does the opposite of what the analysts' previous explanation was. They just tell you something because they know people want a "reason".
They could've easily written "after historic rise and new all time highs, some investors take profit" and it'd also be correct.
It's like a bunch of guys looking at a CPU metric in grafana without SSH access to the server or knowing what it's running trying to figure out the cause. Sometimes it pins at 100% and some guy shouts "it's paging to disk", and yeah, might be, might also not.