It's fairly common. Fans often look for more content related to their favorite shows. Since 'Attack on Titan' has a large and passionate fan base, there are a lot of fanfics available. 'Aot' fans might watch (read) these fanfics to explore different scenarios that the official story didn't cover. For example, they might want to see how a certain character would react in a different situation or what would happen if a major plot event had a different outcome.
There could be various fanfictions. Maybe some that focus on alternative endings, like ones where certain characters survive who didn't in the original. For example, a fanfiction where Erwin survives and leads the Scouts in a different way.
Titanfall was a first-person shooter game developed by Respawn Entertainment and released in March 2014. The game's theme was mecha and sci-fi. The main plot was about the conflict between the development of mankind and other forces in the universe. Titanfall 2 was the continuation of the series and was released on PC on October 28, 2016. The sequels introduced a brand new single-player mode, allowing players to explore the bond between Iron Warder and Titan. In addition, the sequels also added more innovative elements and exciting multiplayer modes, including six new Titans, new Iron Rider skills, expanded customizations, new maps and game modes, and more. There was currently no exact information about Titanfall 3.
It could mean that a person who is a fan of 'Attack on Titan' (AOT) is reading or watching fan - created fictional works related to AOT. Maybe they are interested in seeing different interpretations or storylines that fans have come up with.
One way is to check on popular fanfiction websites. Look for ones with high ratings and a lot of reviews. For example, Archive of Our Own (AO3) has a large collection of AOT fanfictions. You can search for the most popular ones there.
All Titans in Titanfall included Ranger, Sky Map, Giant Demon, Stride Titan, Blazing, Polaris, BT-7274, and Ion Titan. These Titans had different characteristics and abilities in the game, such as different health points, movement speed, melee damage and defense. However, due to the limitations of the search results, more detailed information could not be provided.