This is a consequence of money getting more expensive. When rates are low, investors pile money into non-revenue producing startups in hopes that something will return 1000x. Now rates are up and the smart money is moving elsewhere.
That would only explain drops in future investments, but we're seeing profitable companies with astronomical revenues from their cash cows diving into a massive firing spiral.
More importantly, growing interest rates is not exactly the definition of a downturn.
I don't think this is true at all. Central banks hike interest rates to limit and reign in inflation. It's the exact opposite of what you claimed.