I've seen the app Apollo as the center of the reddit protest (it was mentioned and cited more than any other app in relevant posts). I've also seen many Lemmy clients in development taking inspiration from it.
As a lifetime Android user I've never been able to use it, and I've never gotten a proper answer to "why not just use the official app?" What made it different from the official application and other unofficial clients that consequently made it so popular among Redditors?
Apollo was big in the headlines because its developer was the most vocal about the API changes.
As for why people used third-party apps, it's mostly a preference thing. Something to note is that reddit didn't always have an official app. Everyone using reddit before 2016 had to use a third-party app if they wanted to use reddit on their phone. A lot of the apps we watched get shut down, especially the ones on android (RiF, Sync, BaconReader, etc) have been around for a long time, and had loyal user bases.
Apollo was younger than the official app, but it was likely favored by those who had used Alien Blue (a very popular third-party app for iOS that was bought by Reddit and turned into the official app)
It just worked. You could swipe to vote and to comment. You had the ability to read messages mid thread. It looked good. It was also the spiritual successor of alienblue, an app that was well loved and bought out by Reddit to make their official app which retained very few similarities.
And beyond all that the dev worked hard, communicated with users, and was extremely up front about how Reddit screwed him over with the API change. He’s the one that Huffman accused of threatening Reddit. The other app devs didn’t record their interactions with Reddit.
It was just such a great app. Features such as hiding read posts, auto scroll back when you accidentally scroll to the top of your feed, appearance customizations, and a great dev who took feedback and improved the app based on what people wanted.
Its got a sleek and easy to use UI, is jam packed with features like customisable gestures, no ads, a great media player and (I think) lots of accessibility features.
It’s also wonderful that the dev loved his app and continually updated it
It just has so many unique features. Like sharing a comment or post as a screenshot including a customisable number of comments above it and the post itself. Very useful for quickly sharing or saving comment chains with context, without fiddling with collapsing comments and cropping. Or categories for your saved posts and comments so you could organise. A reminder function built into the app. A subreddit watcher that alerts you whenever certain keywords were posted in a sub. And many more. Lots of things that required more than just developing an app to access an API and display stuff. Gestures were the best I ever used. UI was clean and useful without fiddling with customisation. I was on Android until last year and tried many apps, Apollo beats them all.
But I think it was at the centre of attention because the developer is very responsive and Apollo is the app for Reddit on iOS. On Android you have users spread out across Sync, Boost, RiF, Joey and many more.
The official app is just featureless in comparison. I’m left-handed and you can’t even move the pictures of the posts to the left in compact view so I can access the picture/link/Video without reaching all the way across my phone. Might sound insignificant, but it’s something very simple that every Reddit app I used had and a deal breaker for me.
I know your asking about Apollo but I'm going to be the idiot who chimes in even though I used Reddit is fun. I used RiF because the native app was annoying and slow, I also didn't want to see full screen images as I scrolled. RiF would give me a clean list of the topics from my favorite subs but not load full screen images so I could scroll through faster looking for the subjects I wanted to read/see at that moment. I just felt like I could find more of the topics I wanted faster than with the native app which also didn't exist when I started using RiF. I'm using liftoff now and I'm annoyed at the images loading but I imagine there will be something that's "cleaner" (by my standard) or a way to customize liftoff.