It could also be a situation where Harry is trying to make a desperate bargain. He might offer something to Voldemort in exchange for his help in saving his friends or the wizarding world. Maybe he has some information about a powerful magical artifact that Voldemort desires and he uses that as leverage to get Voldemort to fight against a common enemy.
Perhaps Harry discovers some dark secret about his own past or powers that he thinks only Voldemort can help him understand. For example, if he finds out that his connection to Voldemort is more complex than he thought and that Voldemort holds the key to unlocking or controlling certain aspects of his own magic.
Perhaps Harry has a plan to outwit Voldemort in the long run. By seeking help, he can get closer to Voldemort, understand his weaknesses better, and then use that knowledge against him. It's a risky but potentially effective strategy, like a spy infiltrating the enemy's camp.
At first, it would be extremely tense. Voldemort would be highly suspicious of Harry's motives. Harry, on the other hand, would be very cautious as he is approaching his mortal enemy. But as they start to interact more, there might be a grudging respect that develops if they find they have common goals.
Perhaps in this fanfic, there has been some major plot twist that makes Harry believe that bowing to Voldemort is the only way to save his friends or the wizarding world. For example, Voldemort may have threatened to kill all of Harry's loved ones if he doesn't submit, and Harry is sacrificing his pride for the greater good.
Perhaps Voldemort discovers that there is a greater threat out there. In the fanfic, it could be that another dark force is emerging, and Voldemort sees Harry as an ally of sorts against this new threat. So, he decides to protect Harry in order to deal with this common enemy.
One reason could be a desire for revenge. Maybe in the fanfiction, Voldemort has done something even more heinous to Harry's family or friends, driving Harry to take extreme measures.
Maybe Harry discovers something about his past, perhaps related to his parents, that only Snape can help with. Snape was closely associated with Harry's parents. He might know some secrets or have some information that could help Harry understand a family mystery or some hidden power within him.
In such a fanfiction, Harry might go to Voldemort to try and reason with him. Maybe he believes there's a chance to end the war without more bloodshed. He could offer Voldemort a way out, like exile instead of death.
The most obvious consequence would be that Voldemort would likely betray Harry. Voldemort is evil at his core, and he would probably use this opportunity to harm Harry or gain more power. For example, he could steal Harry's magic or use him as a pawn in a new scheme.
A plot twist might be that when Harry goes to Voldemort, he discovers that Voldemort has a secret weakness. Maybe it's related to his family or some long - forgotten magic. Harry then has to decide whether to use this weakness against Voldemort or try to redeem him. This would add a whole new layer of complexity to the story. Another aspect could be that there are other forces at work, like a third - party wizard who is manipulating both Harry and Voldemort for their own gain, and Harry has to figure out who this is while dealing with Voldemort.
One possible reason could be that Voldemort sees Harry as a symbol of innocence that he wants to corrupt. Just like how he enjoys toying with his enemies, treating Harry like a baby might be a way to belittle him and make him more vulnerable in his eyes.