OP, I spent most of the first 3.5 episodes of Season 2 thinking about punching Wilhelm in the nose. He is MESSY in S2, chaotic, and hurting, and refusing to acknowledge that he has hurt someone he loves.
I think it was an interesting choice by Lisa and the other writers to make Wille react so badly in S2, and try to run roughshod over Simon’s clearly stated wishes. After all, Wille is the protagonist. But just because he’s the protagonist doesn’t mean he’s perfect. Everyone in this show is flawed, including Simon and Wilhelm. And being in love doesn’t magically turn someone into a better and more mature person. We saw that both with Wilhelm’s response to Simon dumping him, and in Sara and August’s romance.
But one thing I did like about Wille treading all over Simon’s wishes is that it did not work. It didn’t bring Simon back to him. What did bring Simon back was Wille finally acknowledging that Simon had stated multiple times he wanted to move on, and Wilhelm finally accepting it. And being a good person about it.
In 2.04, Wilhelm accepts Simon’s new relationship (actually situationship, but Wilhelm doesn’t know that) with Marcus. He is pleasant to both Marcus and Simon at the ball, and treats them like a couple. When Simon is weirded out by this and confronts him, Wille says flat out that he’s stopped chasing Simon. He finally gets it, Simon has moved on, and the most loving thing he (Wille) can do is let him (Simon) go.
And that’s what brings Simon back to him, not all Wille’s manipulative sturm und drang in the first 3.5 episodes. He had to let Simon go, and he did. Eventually.
All that said, I feel empathy for Wilhelm even as I dislike his behaviour. He knows what it’s like to be betrayed, because he’s recently experienced massive betrayal not only by his cousin but also his own mother. And I think Wilhelm’s brain just refuses to process that he too is a betrayer, that he has hurt Simon in the same way Kristina and August hurt him (Wille). It’s too painful for him to deal with the idea that Simon must be in as much pain as he is. And what’s more, that Wille is the one who caused that pain.
So Wilhelm spends 3.5 episodes in denial that he’s hurt Simon. Because he doesn’t want to group himself with Kristina and August. It’s not healthy behaviour, and it’s not supposed to be. And importantly, the narrative doesn’t reward this behaviour of his. The more he pushes Simon, the more Simon retreats from him. Only after he lets Simon go does anything positive happen in terms of mending their relationship.
Plus, Erik’s death is still very recent, and the whole situation is a complete mess.