okay but literally I can’t stop thinking about this -
it is of course possible that Draco would have gotten the Death Eaters into the school some other way if the Vanishing Cabinet hadn’t created the perfect opportunity, but it wasn’t looking likely.
so like, it’s reasonable enough to assume that Dumbledore’s death (at the hands of Snape specifically, obviously I know he was going to die soon enough from the curse, but the timing does make a difference so I’m still focused on this) occurred because of the Death Eaters getting into the school. the reason the Death Eaters were able to get into the school was because of the Vanishing Cabinet in the Room of Requirement, which Draco repaired.
the Vanishing Cabinet ended up in the Room of Requirement over the summer of 1996, presumably (reasoning for this is in the next paragraph), and Draco discovered it there sometime in his 6th year. but the only reason he had even known what it was, and what it could do, was because he had spoken with….
Graham Montague, a Slytherin who was in 7th year in 1995-1996 (when Harry & co were in 5th year). Montague was shoved into the Vanishing Cabinet in that year by Fred and George Weasley, because he was a part of the Inquisitorial Squad and was presumably about to take points from the Weasley twins for doing something disruptive. and we know that Montague got stuck in a limbo between the two connected cabinets, due to one of them being broken - he could hear things being discussed in Borgin & Burkes, which is how he was able to let Malfoy know that the other “end of the tunnel”, or basically the other cabinet, was in Borgin & Burkes (which, Draco would already have seen as a 12-year-old, in the summer before his 2nd year, when he visited the shop with his father - fun fact, Harry hid in that exact cabinet while Lucius Malfoy was transacting with Borgin).
Montague would never have had this experience at all if the cabinet hadn’t been broken in the first place. but in fact, we know exactly how, when, why, and by whom the cabinet was broken.
it was in the fall of 1992, when Nearly Headless Nick observed that Harry had gotten in trouble with Filch, and prompted Peeves to drop that very same cabinet from a large height in order to cause a distraction for Filch, allowing Harry to get out of trouble.
why was Harry in trouble in the first place? because he was “tracking mud” in the corridors.
why was he tracking mud in the corridors? because Oliver Wood had had him out on the Quidditch pitch all day even though it had been literally storming outside. so Harry came into the castle drenched and splattered with mud.
Dumbledore literally died because of how obsessed Oliver Wood was with winning the Quidditch Cup.
thank you for coming to my Ted Talk.