There's a self-regulating mechanism that keeps the network running so that it's not as fast as the fastest validator (as that would make attacks too easy) nor as slow as the slowest validator (as that would provide poor performance). But Ripple has never claimed on ledger transactions rates that high. To get to 50,000 TPS, you need to use off-chain scaling schemes like payment channels.
This is a fundamental scaling limit with all public ledgers that try to create fungible tokens. Every full node must process every transaction and thus if you try to get the number of on chain transactions very high, you impose high bandwidth, CPU, and storage costs on everyone. (You can trade off some fungibility, as IOTA does and as some sharding schemes do.)