They may have changed it because it's closer to the book. I believe that the reason it falls in the first place is to create a diversion so that he can take Christine. I assume Andrew Lloyd Webber changed so that he could have a dramatic Act I finale.
I'm okay with the change, except that, I guess they must have changed the words in Masquerade ("to a prosperous year, to the new chandelier" and "remember there are worse things than a shattered chandelier") and i like those lines
"No thoughts within her head, but thoughts of joy.....no dreams within her heart but dreams of love."
