The sudden surge in popularity for JAR game repacks boils down to three main factors: 1. Pure Nostalgia
However, it is important to note that most JAR games are still under copyright. While many of the original developers have gone defunct, downloading repacks of commercial games often falls into a legal gray area or constitutes piracy. For those looking for legal alternatives, several "indie" Java developers still host their original files on personal archives. What Are Reloaded Games and Repacked Games? - MakeUseOf jar games repack