Java is (or at least used to be) one of the first languages new programmers started with.
Making it very accessible to create new mods.
I haven’t modded as of yet but I started off with Java and am now a C# Dev and the transition wasn’t too hard since most of the same principles apply to both languages. Unity games, that are often written in C# to me are the most moddable ones, especially considering that there’s a ecosystem for Unity mods out of the box
Minecraft. Runescape. Mindustry. Slay the Spire. Project Zomboid. Doodle Jump. Shattered Pixel Dungeon. Delver. Lots of mobile games. Also It’s rediculous to say Java is inappropriate for games when C# is used for games via Unity (unity is the value proposition there - c# is very similar to Java)