>Hollow Knight had been massive, and their plan at the outset was to build a smaller world for Silksong. To ensure that the game felt just as deep, they'd implement an elaborate quest system that would offer the player reasons to backtrack and revisit old locations. In contrast to Hollow Knight, which had a single town full of shops and characters to meet, there would also be multiple towns, each serving as a hub for quests.
>"Even at that point we were recognizing that it was going to become another giant thing to rival the scale of Hollow Knight or probably exceed it," Gibson said. "And then because of how we work, obviously the world ended up being just as big or bigger. And the quest system existed. And the multiple towns existed. Suddenly you end up six, seven years later."
>it all came down to their development style, which may have been too much fun. Gibson and Pellen — who were joined by programmer Jack Vine, composer Chris Larkin and a few contractors who helped with programming and testing — started off by designing the core gameplay for Hornet, the game's slick protagonist. From there, it was easy to implement and test out new ideas, even as the game grew bigger.
TLDR: They had too much fun making the game that 7 years went by in a blink

https://www.bloomberg.com/news/newsletters/2025-08-21/why-silksong-team-cherry-s-sequel-to-hollow-knight-took-so-long-to-make
https://archive.ph/wip/pGucD