So, it was an individual who dropped out of a YC team? Or was it an entire YC team which dropped out? The former is common (although often pushed...); the latter only heard of once personally, except for the one famous "YC retraction (storenvy)". (someone in YC S11 had an idea for a payment system, got in, realized it wasn't viable, so dropped out before the beginning of the program; honestly probably should have stayed in and explored things in Bitcoin, etc., but that's with the luxury of hindsight).

I don't think founding a startup is ever "easy", but it's incredibly fun for a lot of people.