ETH whales have been transferring large amounts of Ethereum to CEX for some time now, all for impressive reasons.

Sell-Off for Dumping?

     These are not small transfers that count towards using CEX's Earn program. Ethereum is now PoW; it is possible to make passive income by staking just 32 ETH, so transferring large amounts of ETH to CEX is probably to sell it, which is a dumping process.

Effect of Vitalik's fear?

     Vitalik Buterin is afraid to stake all his ETH, while other PoS projects encourage people to stake all their tokens, so naturally some people may turn from ETH to other projects. For some time, ETH has been competing with tokens like SOL, MATIC, SUI, SEI etc in terms of popularity and usage.

Dencun Effect of safety?

     Ethereum's 'Dencun' upgrade is currently going on testnet. It is possible that Stakers are fearful of the possibility of their tokens being stuck somewhere, so they are transferring their Ethereum to a trusted CEX for safety. Later, they might withdraw their ETH to stake again.