Pokémon Alpha Sapphire and Omega Ruby were released six years ago for the Nintendo 3DS. There hasn't been any fanfare about either game receiving new content at any point recently, and there aren't remakes coming. So why has Alpha Sapphire, specifically, been trending on Twitter over the last day or so? That's a difficult question to answer.
It appears that there is no real answer to the question, as it seems that, like many other trends on the social media platform, there isn't one. The trend popped onto the radar likely as the result of people discussing how much they love and appreciate the games while we're all stuck inside of our homes for the long haul. A quick stroll through the trending topics category proved that it was mainly comprised of people reminiscing and offering their thoughts on the system.
Alpha Sapphire and Omega Ruby were exciting entries in a series that had been stagnant for a while and introduced the Weather Trio Pokémon including Groudon, Kyogre and Rayquaza. Not only did they come back into the spotlight when these remakes hit the scene, but they got new Mega evolutions and Primal evolutions that gave trainers even more reason to jump back into the game, even after being gone from some time. Primal Kyogre was especially popular at the time.
The games featured redesigned characters, revamped set pieces, and intriguing design decisions that simply improved the series in significant ways, giving some important characters new gear and looks and even purposes for doing what they were doing with their Pokémon. It's no surprise why the games were so well-received, but back to the topic at hand, there was still no real explanation about why Twitter was suddenly awash with people thinking about these exciting 3DS releases. That's kind of how Twitter works though, weirdly enough, with a bandwagon effect happening here and there when a group of individuals start chatting about a game or topic enough.
The most recent Pokémon releases are, of course, Sword and Shield. They'll be getting their own DLC later this summer. By then, hopefully, we'll be able to leave our homes and chat about it with each other in person instead of making it trend on Twitter.