Entrepreneurs know when they're making a bad decision, whether consciously or not.
[Edited for brevity. No disrespect, but hate to see a Developer give up on their independence]
Perhaps "I hope this new gig works out for you right now, but really hope to see you running something of your own again at some point in the future"?
Same with countless other jobs, such as working at Facebook, Google, Amazon, Snapchat, etc
He'll come back to the dark side soon enough and build a sustainable business model (with the benefit of experience at Stripe, of course) :-)
If this is anything like how the company I'm at is doing internationalization there will likely be pushing (and some implementing) technical requirements to make the product culturally accessible. There will be B2B, and in this case B2Gov discussions. I'm sure he will also be heading up finding office space and hiring others to do the work.
This is a very likely a senior management position in addition to I'm sure a senior technical position.
Joining a larger organization can provide the opportunity to accomplish things that would be difficult or impossible on your own. And if it doesn't work out, or eventually becomes disappointing, it's still possible to hop back on the entrepreneurial horse and ride off into the sunset.
People tend to see things through the lens of their own thoughts and experiences. The author of the post in question is probably just trying to provide advice based on how they'd feel in a similar situation. The wording probably made it seem more abrasive than it was intended to be.