IMHO, the main reason why Spring is huge is because it has grown organically to encompass many of the business cases/issues that one may encounter in both depth and breadth. So the http framework supports almost everything you may ever need and there is integration with every database, middleware, infra like kubernetes. (One can debate about the quality of all the lesser used modules but the main modules are pretty okay.)

On the other hand I have used Quarkus which was great until it wasn’t because a certain http feature wasn’t supported or we needed integration with an unsupported database. In enterprise that is enough reason to just choose for the batteries included option and lift along on improvements of the main framework.