Apple dropped support for 32-bit components. While Premiere CS6 is a 64-bit app, its installer and several licensing components are 32-bit. This means it will not install or run on modern macOS versions without complex workarounds like virtual machines or "retro" partitions. Conclusion
If you have the original CS6 Mac DVD, you can copy the .dmg to your hard drive. No download needed. This is the most reliable method.
Disclaimer: This article is for informational purposes. Always adhere to software licensing agreements. Adobe, Premiere Pro, and Mac OS X are trademarks of their respective owners.