The longevity of 1.7.10 is driven by its unique position in Minecraft's technical development: Java Edition 1.7.10 – Minecraft Wiki
By late 2014, Minecraft Forge had reached a state of near-perfect stability on 1.7.10. Modders could write complex code without constant refactoring. This meant huge mods like Thermal Expansion , Thaumcraft 4 , Applied Energistics 2 , Botania , Blood Magic , and GregTech all flourished together.