I've been a little grumpy lately that so many webtoon adaptions of novels change things for no reason, but I'm okay with this one!
In the novel, Grandpa actually fell DOWN those stairs, with Tia holding onto him. He remained conscious through sheer willpower and made sure that he cushioned her fall, because he didn't want Tia to get hurt again because of him.  ╥﹏╥
So just seeing him collapse at the top of the stairs, instead of falling down them, is a vast improvement. I don't like Grandpa Lombardi getting hurt.  ╥﹏╥