There were many interlocking pieces of evidence already pointing to the truth of Q == V (I think readers were actually chastising Harry for not figuring it out earlier at some point); the perfect timing of this particular incident was simply the part that happened to break Harry’s voluntary suspension of disbelief enough for him to actually start trying to piece it all together.
As someone pointed out on Reddit, it’s pretty suspicious that Harry figured everything out almost immediately after Snape hit him with a “Dispel Confusion”.
This would also neatly explain why Quirrelmort didn’t see this coming “Snape does his level best to help Harry Potter” does not seem like the kind of outcome Q would consider very likely, so his overly complicated plot going off the rails there is perfectly reasonable.
There were many interlocking pieces of evidence already pointing to the truth of Q == V (I think readers were actually chastising Harry for not figuring it out earlier at some point); the perfect timing of this particular incident was simply the part that happened to break Harry’s voluntary suspension of disbelief enough for him to actually start trying to piece it all together.
As someone pointed out on Reddit, it’s pretty suspicious that Harry figured everything out almost immediately after Snape hit him with a “Dispel Confusion”.
This would also neatly explain why Quirrelmort didn’t see this coming “Snape does his level best to help Harry Potter” does not seem like the kind of outcome Q would consider very likely, so his overly complicated plot going off the rails there is perfectly reasonable.