If I had to hazard a guess this might be a cost-cutting measure on Stripe's part similar to cuts on content marketing that other companies have done. DigitalOcean divested from CSS Tricks [0], and there was an article earlier today about Amazon shutting down DPReviews [1]. Maybe the Stripe founders gave the IndieHackers folks a chance to spin it off again as opposed to shutting down.
The two founders/employees probably cost $600k/year and at this point, Stripe is so well established that IndieHackers sponsorship probably doesn't move the needle much on Stripe adoption anymore. They probably just mutually agreed to cut ties and the founders will have control over their own revenue / income.
$300k each sounds high. I don't believe they had reports. It was its own fiefdom. Probably closer to ~$200k. I don't believe they are Bay Area–based, either, where 300 might make more sense.
A stripe software engineer in the US is easily making $300k, including equity, unless they’re a new grad. Add another 10-15% for their benefits and total cost to Stripe.
It seemed like a standard acquisition / acqui-hire. Buy out the business, Stripe owns it, the employees are paid like Stripe employees. Access to codebase is tangential, big tech co codebases are already very segmented off into tons of repo's with different access permissions. Ultimately, this is just conjecture.