and he bought a second laptop to have multiple screens, just for crypto.
If people only need multiple screen, they would buy additional monitor which is cheaper than a laptop. So it's likely he bought it for another reason.
My question would be: does he obviously hiding a lot of earnings from me in day trading, that he would do from Mars to December? Or is he legit to say he is just waiting all this time the good time to sell BTC when it will be a good time(with a new laptop just for crypto that he bought, not a expensive one, but anyway)
Without additional information, we only can say "we don't know" or make baseless speculation. If you want to find out the truth, force him to show proof from how the money is moved, where/when he bought Bitcoin and how he store the Bitcoin.