If you're a Trinitarian this is already solved - God willed it in the flesh which he incarnated into. Jesus would've just been the human flesh that God used, it would be sacrificing a humanized, representation of God.
That's not Trinitarian. It's... something else. In the Trinitarian formulation, the Father, Son and Holy Spirit are all separate persons, and all co-equal, and are each God individually but also God when taken together.
If you're a non-Trinitarian, it still can be solved. Jesus was anointed, it wasn't God's demand, Jesus knew it would happen and let alone wanted it to happen; he's an altruistic superman.
That doesn't make him altruistic; it makes him masochistic: "I needlessly hurt myself to show I love you." It would be psychotic.
In some versions of Christianity.
In many of them, Jesus spent the time from the Crucifixion to the Resurrection in Hell, however, I've heard two versions of what was supposed to have happened there:
- at that point, Hell was just a "waiting room" and not a place of suffering and punishment (since in their view, that comes after the Final Judgement). He spent the three days preaching and ministering to the souls that died before he came to Earth so that everyone would have an equal chance of accepting Christ and salvation, even the people who were born too early to hear about him in life.
- Hell was a place of suffering and punishment, and over those three days, Jesus was punished for all the sins of humanity.
Why would it imply God is evil if it were necessary?
Because nothing is necessary to an omnipotent God, so if Jesus' suffering is necessary, it would only be because God made it necessary. God could have chosen a suffering-free option, but instead chose this one.