Ya’ll know how Bruno’s room has, like, an UNREASONABLE amount of stairs? Even Bruno comments on there being too many stairs. Why would a room made specifically for him be so full of stairs?
My theory is that the rooms grow to reflect the mental/emotional state of the person who lives there. We see a glimpse of this with Isabela, who has a GIANT WALL OF FLOWERS that change perfectly in sync to mimic her dancing. Sure, you could say that’s partly her power, but I think it’s also partly her room reacting to her. It had been pristine and sculptural before because that was the way she felt she needed to be, but it burst into riotous motion as soon as she began to recognize her freedom to be creative.
So my theory about Bruno’s room and all those stairs is: there weren’t as many stairs to begin with. But as Bruno got more and more estranged from his family and the town - both from his own misuse of his power (we see his mischevious streak when he accidentally spoofed Pepa’s wedding, and he says himself that he has a lot of apologies he needs to make) and from people misunderstanding and villainizing him - the stairs grew. More and more stairs to signify his feelings of distance from those around him. A broken bridge at the top to indicate that final “severing” of contact when he “went away.”
We also see signs that the house was cracking long before Mirabel. All of the cracks Mirabel sees heal themselves as she returns to some kind of equilibrium or comes to a better understanding of a family member. Mirabel is trying to remain open and get closer to her loved ones (albeit begrudgingly in Isabela’s case).
The only cracks that have to be spackled over are the ones in Bruno’s hideaway. He is back there spackling all these cracks because there was no healing for them yet. Because he was avoiding his family and thus couldn’t resolve the “cracks.” That’s not to say it was all his fault; reconciliation is a two-way street, both sides need to be willing. But I think it’s a really good example of how cracks under the surface of relationships will stick around even if we “spackle” (hide) them, unless we find a way to deal with them.
Bruno needed to address the issue instead of hiding from everyone and wallowing in his misery. He needed to move forward to truly heal the cracks, and Mirabel opened the way for him to do so. Thankfully, in this case, that forward movement involved reuniting and reconciling with his family. For some people, it may involve forgiving those who hurt us and allowing ourselves to move on with our lives. (But even in those cases, it’s good and healthy to leave the door open for reconciliation in the future. Alma’s change of heart is a beautiful symbol of how even the hardest people still have the potential to soften and grow.)
All that being said: I have a feeling that now that Bruno and his family have reconciled, his room is gonna have significantly fewer stairs. =)