[InclinedPlane]

You need to understand that software developers aren't like factory workers. The difference between a factory worker putting in 1500 hours of work in a year and 3000 hours of work in a year is maybe that 2x more widgets get made or something. It's easy to just get another shift of workers to come in and get the same total widgets made, no big deal. But software development isn't manufacturing, it's a creative, even artistic venture. Making software is like making a movie. The difference between working 1500 hours in a year and 3000 might be the difference between making "Sharknado" and "Citizen Kane", meaning, the difference between making an incredibly compelling product that has a huge social and economic impact or just some throwaway crap that will fade in relevance quickly over time.

Making great software tends to require extremely talented developers who are extremely engaged in their work. And that tends often to result in devs working long hours as a natural consequence, though that's often not strictly necessary to produce good results (despite what I said above, though it is often strongly correlated). Regardless of how many hours are put in, when there's a collision between the passion and engagement in the work from the individual on the one hand and the rewards, recognition, and guidance coming from management and the rest of the company the result can easily be burnout. Burnout can happen even if you're only working 20 hours a week, it's not about some trivial reaction due to overwork. It's about traumatic interpersonal experiences. It's about being engaged strongly and passionately and either being overused or misused.

Alternately, think about it in relationship terms. A passionate dev has fallen head over heels in love with the project their working on. So much so that they dedicate a lot of their life to it. If they don't see that love reciprocated, or if that love is used in service of an abusive or dysfunctional relationship then it will cause the individual significant emotional trauma and heartbreak which is manifested in the form of "burnout".

Again, burnout isn't necessarily overwork, it's the equivalent of heartache and emotional trauma in business relationships.