K-pop has been around for decades; however, they started getting more popular with PSY- Gangnam Style released, and it is the most viewed K-pop Music Video worldwide. BTS - the biggest K-pop boy group, has opened the doors for many new global fans and has increased tourism. They contribute to a total of 3% of their country's GDP. Due to its popularity, people started getting pretty interested in Korean culture and cuisine. The tourism industry in Korea witnessed skyrocketing growth as well because of global fans.
Nevertheless, when the pandemic hit and the whole world shut down, the fans couldn't attend the concerts and visit tourists attraction in Korea. That's when the trend of purchasing k-pop merch started. Many k-pop fans are social media influencers, and they show the before and after of their room that they decorated with all the kawaii (cute) k-pop merchandizes. Multi-stans (those who support more than one band) like to collect all their favorite idols' new and previous albums and arrange them beautifully on the bookshelf.
Every group has their merch like BTS has BT21 (the whole group is featured on this beautiful plush throw); they all have their respective characters. Hence, Fans take pleasure in keeping little things that show their love and support for their idols. Additionally, maintaining photocards in transparent phone cases or wallets is a global trend among fandoms. Fans keep purchasing albums until they get the photocard of their bias in the group; therefore, increasing the sales.