@EzWeeb
Well this series in particular is popular for several reasons:
1) It helped popularize the "Reincarnated Villainess" genre/is one of the OG ones
2) It did something different with the genre by making it lighthearted, heartwarming fluff instead of focusing on the typical revenge story
3) It appealed to all demographics instead of the typical shoujo & josei demographic
4) Really likable MC who is not OP strength/magic-wise but just lovable and charming
5) Currently has an anime airing so anime watchers come to look at the manga
And yes this series is
VERY popular (started off as a web novel, then got 9 LNs, own manga. manga spinoff, own anime. and now an anthology).