I'm always confused as to what factors actually contribute to a CryptoCurrencies capacity?

If you guys could provide a run down on what do the following blockchains do under the hood to have this TPS and what it's
limitations are in that regard than I'd appreciate it:

Bitcoin (7 TPS)

Ethereum (20 TPS)

IBM Blockchain (1000 TPS)

Ripple (1500 TPS)

Cheers.