Why my startup failed and other life lessons

In late October 2019 , I decided to leave the startup which I cofounded with my college senior + batchmates four years back. My wife, who was also working with us at that time - too left with me. And on our 3rd marriage anniversary, we both were unemployed and directionless.
Although that brought a full stop to my entrepreneurship break, whenever I mention about my startups with new friends, colleagues (or in interviews) - they always asked me why it failed.
As it was not a single, straightforward reason - sometimes, I just respond these questions with cliche one-line answers like - we could not scale our sales funnel, or our revenues were low and funding dried up. Because, most of them were not really interested to know the whole reason and just asked for formality.
Now, when I look back and try think about it - t