From the article:
A volunteer-made project that fights bots on Reddit is shutting down. BotDefense, a tool that helps fight bots in more than 3,600 subreddits and has nearly 150,000 accounts on its bans list, will be going away.
As for why: The community of users and moderators submitting accounts to us depend on Pushshift, the API, and third-party apps. And we would be deluding ourselves if we believed any assurances from Reddit given the track record of broken promises. Investing further resources into Reddit as a platform presents significant risks, and it’s safer to allocate one’s time, energy, and passions elsewhere.
It’s the money from Reddit’s IPO launch that he is after, the API changes are about sending a message to investors that their needs will come first.