I am not a finance guy; this is my kindergarten-level understanding of the situation:

When the interest rates were hovering down around 0%, it was a no-brainer for VC firms to shotgun money out to everyone who walked past their office building. Most VC money doesn't come from some rich dude's pocket; it comes from banks and hedge funds and other deeply-market-tied entities. If any one startup they've invested in can win the profit lottery, the VCers will massively beat the rate of return they'd get for anything else. One big success can cover a dozen small failures, and, anyway, a business isn't a failure until it's a failure.

Now that interest rates are rapidly moving higher, those startup investments are less of a good deal. VC money is more expensive. VC firms are starting to close out their positions on start-ups that aren't beating them market, because they want to stick their money somewhere more reliably profitable.