Fundamentally, there is too much money (interest rates are too low, money is too cheap) chasing too few returns (too many startups are ultimately just bad business ideas).
Remember when everyone was talking about a bubble in '14? It wasn't a bubble in the end-point of these startups, it was a bubble in their initial creation and funding, and this is the consequence of that bubble: decreased returns, illiquid assets, the end of the 3-year cycle time without the values that were expected.
The biggest threat is your third point, as it makes the inevitable bust far more painful if you're able to paper over the long-term issues with short-term money. And the secondary threat is that there is no bust but this just continues on as a slow death, which slowly drains VCs of investment funds from other funds (pensions, etc.), which makes their money more expensive, which sucks out more money, repeat.
Remember when everyone was talking about a bubble in '14? It wasn't a bubble in the end-point of these startups, it was a bubble in their initial creation and funding, and this is the consequence of that bubble: decreased returns, illiquid assets, the end of the 3-year cycle time without the values that were expected.
The biggest threat is your third point, as it makes the inevitable bust far more painful if you're able to paper over the long-term issues with short-term money. And the secondary threat is that there is no bust but this just continues on as a slow death, which slowly drains VCs of investment funds from other funds (pensions, etc.), which makes their money more expensive, which sucks out more money, repeat.