What are their motives:
To pump and dump.
Or
Pump and get the price of BTC and investors confidence up. In this instance I would hope the intentions are good!
I think the whales are scared. If the price of the crypto market continues to fall, many will probably retreat from the market and, of course, only the whales will stay. So they will not be able to make a lot of money, and that is why they inject money into the market recently