Reddit used to have an open API. A lot of mobile apps sprung up to access reddit over the years, with different features. Reddit gained a lot of loyal members through users of these apps, but couldn't make ad revenue off them. Reddit decided last summer to start charging a lot of money to these app developers to continue using the API. A few of the apps started a for-pay subscription model to continue operating, but many just shut down their apps. Many redditors and Reddit mods revolted, because these apps made the site usable (some of them offered advanced mod tools, etc). We protested, shut down subreddits temporarily or permanently, deleted our accounts, moved to new platforms (like lemmy/kbin), etc. This was basically a move to maximize their ad revenue while Reddit positions itself for an IPO. It was really not cool.