Dark Inc investors signed up for a unicorn ($1B company) or better. They didn't get that, and they aren't interested in shares in a small business making programming languages. So they want to shut it down, they're not interested in funding it, and actually would much prefer to not have shares than to have shares in it. They are also interested in their reputations, so having a "soft exit" is better than a hard shutdown - usually that's an acquihire where they get a bit of cash back and get to say "we succeeded" but they also don't want to damage their reputation by shutting down products that are in use.
Meanwhile, the new founders of Darklang Inc are interested in building this cool language, and so want a (possibly small) business making programming tools while continuing to make a living. That company needs money to run until it gets revenue.
It is much simpler and cleaner to sell the assets than to sell the company (many acquisitions are structured this way). It's not just money in vs money out, it's what are the needs of the stakeholders. It's in the interest of both Dark Inc investors and Darklang Inc founders for Dark Inc to sell assets and shut down. Dark Inc investors are relieved of reputational liability and can close their books on the investment, and Darklang Inc gets a clean start.
In this case there's more money in than out - that money isn't just for buying assets though, it's for running the company for several years.
Hope that addresses the question!
