How does msfvenom generate such a powerful payload despite being so small in file size?

[Morsmalleo]

Pretty simple question, how does msfvenom generate such a powerful APK payload despite being so small in size?

Please Read

metasploit APK payloads contains only 4 files as seen in the screenshot below of the Java files belonging to This section of the Rapid7/metasploit-payloads repo...

...yet the payload is actually quite powerful due to the extensive amount of things we can do after a reverse connection is received, despite the payload being so small and despite the fact that there are only 4 files here, I would like to know how this is possible if anyone knows?

I've noticed that Proguard plays a role in minifying the APK payload size according to the screenshot below of the Proguard.cfg file in This section of the metasploit-payloads repo, but that just obfuscates/minifies what's already there (i.e the Java files pictured above).

I've done quite a lot of homework on this through searching code in the metasploit-payloads repo, but I couldn't find anything.

Any answers on this would be great, I'm trying to achieve similar results with a payload of my own (i.e minimal files, powerful/large results)