Let's see if I can summarize all of these:

1. Product not good enough.

2. Spending too much.

3. Running out of money because not enough revenues or funds raised.

Did I miss any? There's a "losing motivation" element but that's usually a result of the other 3.

I think almost all of them were about product-market fit when you come right down to it. Money issues are mostly a signalling device.

Yes. Basically they ran out of time before the product was used enough to bring in sufficient revenues.

Let's face it, product-market fit is hard.