>>282123066
It was probably a right place right time thing. Chaika herself has a good mix of stupid, cute, and capable that feels unique to her, compared to other memeable girls that fall more towards the cute and stupid side. It helps that she has a funny voice. The rest of the core cast was also likeable enough that they have their own memes, like Fredrica puke and "I am cum".
I think people are just nostalgic for the early mid 2010's era now, where anime was just hitting the mainstream, but wasn't full of normalfags like it is today. Lots of anime that would either define genres or have a long impact on anime culture like AOT, JoJo, Fate, and Madoka. Before SAO brought the Isekai plague upon us.