Wow, Marco really does hate the idea of having employees. In this case, he accomplished the goal of many small business owners: a successful product where a trusted employee handles the day-to-day operations and the owner can be hands off and take the profits. But his immediate reaction is to sell it because he doesn't want to be a product owner, he wants to be the entire business.
I am so confused as to how you came to all these conclusions. To me, it seemed pretty clear that he wants to develop things, and to program as his job, rather than run a business.
"without doing much of the kind of work I actually enjoy."
You seem to be saying the same things as I did. My point was that is very unusual for a small business owner, to sell a profitable business because it's not taking up enough of your time.
The reason a lot of people want that is they want a passive income to give them security.
Given the success of instapaper and the fact he'll have done fine out of Tumblr, I suspect Marco has no need for that and would rather devote his time and attention (something can be distracting even while taking little actual time) to something he'd be happier doing.
I think he's probably underestimating his responsibilities and overestimating those of the other employees. It also sounds like he has to deal with things he doesn't want to deal with, not that he has nothing he has to do.
The details of the sale aren't public either, and he's now an "adviser" to The Magazine. He may still have some equity in the company. One could also analyze the profits from a sale compared to estimated profits down the line, and feel that they would rather cash out now, to pursue other interests. A lot of "savvy" business-people and businesses divest themselves from businesses that they feel have outgrown them or are not a part of their core business model.
I would agree with that. I would guess the initial draw was developing the iOS app and the web app, and the fun image of being an editor. Except that being an editor was a lot of work, without that much fun parts. So he outsourced the editing, but now all that was left was the business side, like writing checks, and that is not fun at all. And the apps are done, so no fun there.