A single database/network cannot be the network of networks, which is ultimately the biggest flaw of the Bitcoin blockchain.
The interledger protocol is an overlay protocol which allows innovation on different parts of the network independently from a central governance model.
What role does XRP on the XRPL play in all of this (below) ?
2 main roles.
1.) It acts as a fee so that there is a neural way of charging people for making transactions.
2.) It was built to be a liquidity asset. Also known as the secret sauce of the XRPLedger.