Slack wanted to stay independent, but was unable to compete with tech giants

I agree that after exponential growth founders get a little piece of the puzzle so that they can't make decisions by themselves so that investors push to get an exit.
I believe that the only way to get to this point is to have a different money insertion mechanism like Earnest Capital or Tiny Seeds, but those are few from the amount of dollars needed for this companies to grow.

I hope to see more investors like this to help bootstrap companies to success without losing decision power.

Other thing, that come to mind is that when you hear some founder after long year on the company looks like they get burn out. I remember the story of Freshbooks founder that recently sold most of his shares. When you hear the tough times that those founder undergo without a substantial change that make you think that having 50% of shares that are value X dollars but you can not make use of it, help you to decision the way to go.

Hopefully we can heard Steward talk about his decision soon.