Chapter Two: In Which Dreams Are Decoded
"Harry, you've had these dreams before," Hermione said. "You had flashes of what Voldemort was up to last year."
"This was different," said Harry, shaking his head. "I was inside that snake. It was like I was the snake. . . . What if Voldemort somehow transported me to London —"
"Oh dear," said Hermione exasperatedly. "Maybe someday you'll start using that brain of yours. Why would Voldemort transport you to London only to turn you into a venomous snake and make you bite Mr Weasley? If he could perform such a complex human to snake Transfiguration, why couldn't he just Transfigure a pebble into a snake? Why would he need you for it? Also, how are you important to Voldemort's plan? He can just go into the Ministry himself if he is so powerful!"
They all stared at her.
"This is not even considering the fact that doing all this work would be pretty useless because there is just no point!"
AN: There is a reason why OotP is considered one of the worst books in the whole series by the fandom. It has more holes in it than Swiss cheese! It is canon that Voldemort could have taken the prophecy (it was about him and Harry, so only he and Harry could take it without getting cursed) but was afraid he would be seen.
The problem with that is — the Death Eaters get into the Department of Mysteries to fight Harry and his friends, then so can Voldemort! And he does at the end when Dumbledore and he duel. So Voldemort was basically doing nothing for the whole year, just like every single year in the series.