Fundamentally yes. PoS requires users to stake their coins in order to secure the blockchain. Not enough people staked their coins, they left them in exchanges. This caused the blockchain to become insecure and allowed an attack to happen.

Moral of the story is stake your coins, never leave on exchanges.

Also,

exchanges must impliment the staking of coins deposited in order to secure the blockchain for all PoS coins. Any exchange that does not do this should not be permitted to act as a platform for the trading of PoS crypto as they will fundimentally undermine the security of the blockchain.

As always, the decentralisation of the network and the security of the blockchain must be maintained!

edit* a lower coin maturity will also help.

edit** an upper limit on coinage allowance for wallets would also help.