Earlier quoted context omitted.
Not great when every other share price collapses as they get sold as funds are rebalanced. Almost every stock in VIG is in the S&P.
The "almost" portion of your statement is the entire point, and re-balancing isn't going to cause "every other share price to collapse".
Their impact would be felt across the whole market by their sheer valuation - even if you tried to exclude them specifically.
So yeah, if eg ai crashed and took Nvidia, meta, goog or MS for the ride... You'd have massive impacts all across the board, even if you specifically tried to exclude them from your index, just because of how gigantic it's share on the economy is.
But this is purely theoretical. It can only be considered an opinion until something actually happens - because the market has never been in a situation like this before - no matter what some people may claim.