How does Casper solve the trilemma of security, decentralization, and scalability?

As a Proof-of-Stake (PoS) network, Casper relies on a set of validators to uphold the network. PoS validators do not require the same hardware setup as Proof-of-Work(PoW) networks, allowing validators to be more geographically decentralized and eliminating the centralizing pressures of economies of scale. PoS also enables scalability mechanisms like sharding, a forthcoming feature to allow the network to process multiple transactions simultaneously, improving overall throughput.