The value of Bitcoin would plummet if a large investor sold their entire Bitcoin holdings at once on a single exchange. That is, the trader would dramatically push the value of Bitcoin on that cryptocurrency exchange.
Alternatively, the whale might spread the assets among many exchanges to ensure enough liquidity. After all course, we have no way of knowing whether or if this wallet holding Bitcoin is commencing the transaction to eventually liquidate holdings. It is purely anyone’s guess. Additional rationale for transfer of Bitcoin between exchanges is for safety purposes.