Here's my two shots in the dark to explain this monstrosity:
Retired couple buys one of those workshop/huge garage and apartment combos. They decide to turn the workshop into an event space for weddings.
They add a few conveniences for the wedding party, like a couple extra bedrooms to get ready, and a black and red honeymoon suite. The decor is hideous because retired wife is old af and it looks good to her. Retired husband sucks at DIY, like electrical and room layout, but doesn't let small things like planning get in his way.
Grandson works at a siding company that mainly does B2B installs and often has leftovers. Sometimes he grabs other overage from the project after talking to other tradies, like a banister here and there. Maybe an orphan cabinet base.
Grandson wants to start his own siding business one day so he is happy to practice installs on the wedding rental building.
Alternative: Fundie church does secret child marriages here and the couple that maintains the property is allowed to live there as well. The ugliness of the property is because they're purely utilitarian and just need a facade of wedding shit because it's not really about the wedding as much as it's about keeping it on the down-low.