Bitcoin is a algorithmic protocol released into the wild(cyberspace/internet)
Once this occurred it is free to live forever so long as there are miners mining it and people with wallets making use of the network by transacting.
Those transactions are contain within the blockchain ledger and blocks are released on averaged every 10-20 minutes.
Miners are attempting to discover those blocks by hashing at unimaginable speeds.
When they find one that miners pool is awarded the coins contained within that block.
The majority of the coins(21million) have been found and most were mined by miners using GPU’s aka graphics cards(AMD)
The majority of people who had access to high end graphics cards back when they originally were ported to be able to mine bitcoin were gamers.
So to answer your question the individuals who made out or hold the majority of those bitcoins are gamers and also others young nerds all around the world but most of which are American.