ZIRP allowed a lot of "businesses" to exist that wouldn't in a conventional, competitive capitalistic environment. Businesses in quotes because there was never any reasonable potential for profitability, but it didn't matter because VC money was cheap. Building a sustainable business is hard, playing "startup founder" and having that lifestyle subsidized by VCs is easier.
In that case, (over)engineering was part of the performance art that was required to keep your only revenue source: the next funding round. There was never any incentive to "finish" the product because doing that would put your business model (or lack thereof) to the test and stop the music. On the other hand, as long as cheap money is around you could endlessly "engineer" and pivot and bullshit around, chasing the next funding round and using that to pay yourself/your friends decent salaries.
During the ZIRP era it was all about "engagement" and DAUs/MAUs, then it was blockchain, and now it's all about AI. For those that have run out of grifts, they fold or "incredible journey" and get sold for pennies on the dollar to entities like Bending Spoons that do notice there are bloated engineering teams that can be cut.
