Daniel didn't deserve to die man, he's not evil on his own, he wanted to escape from upside down, he was desesperate, ofc he was going to do bad stuff being desesperate
Personally I think it should have been Will to be targeted. Mike getting kidnaped fells like a result of fan theories about Mike begin last target of Vecna. But here it seems like they gave Will's fear of upside down to Mike. Mike inner biggest fear was loosing all his friends, family and El. Daniel's line's "Youre afraid, for him" makes me a bit confused. Was daniel referancing himself? Mindflyer? Someone else? Idk but to me Mike seems like he either denies that he's scared of asking El to date him or he just has too much in his mind to do so. Changing the lines to "Youre afraid, for her" would make more sense, if they wanted to set up the Meleven ark.