He might not be a fool, but both his business acumen and hers are in question. Piecing together what Cynthia's sister and Cynthia herself has said, she was broke, broke, broke. Child services were going to take the kids (whether it's because she was destitute or an issue with prescriptions is up for debate), and it's likely she was going to lose the house they'd been in. The reason she split the jackpot was because she'd been so broke, the father had been giving her money for food.
So how successful could his business have been if his grandchildren were going to be placed in foster care and none of them had the money to fight to keep them and Cynthia was basically impoverished.
Now we are at after the win, if his business is going strong, why hasn't she gone back to work for him? This is the 2nd time she's been in serious financial trouble and that business hasn't helped.
Maybe they have a big chunk of their share left and they'll help her out. But I wouldn't. She's proven she can't live within her means at any level. She needs to get a job and live on that paycheck. Time for her to start being a financially responsible adult.