For every complex problem, there is an answer that is clear, simple, and wrong.
There are a number of other reasons that (might have) contributed to greater or lesser extent:
* rush to capture users and get acquired (the buyer can worry about profitability)
* race to the bottom by multiple competitors (you might want to be profitable but can't command a high price because others' are artificially low)
* ignoring costs that were rising faster than anticipated (wages, cloud costs, etc)
... and probably many more.
Not saying you're completely wrong, but ZIRP is just part of the picture.