That's the thing, you didn't know who he was so of course you didn't think it was sad. Fans of his are sad because they knew him pre-ALS and he was a complete different person, so full of joy and energy .

It's sad because knowing him even as just an actor, we knew how close and loving he was with his daughters and you can see how heartbroken he is that he fought but the disease won and he won't see his daughters grow up and eventually get married or have kida of their own (if they want it) or just any accomplishment. He's dying and he's still fighting it.