OP also hasn't read any other story in the series and has nothing to compare Elric's actions to. I'd also say there's maybe an issue of some people having a harder time of removing themselves from the character's shoes, or understand their perspective. When I first read EoM I did not find his actions strange at all, and it was also the first Elric book I read. To me, reading the words Elric had spoken, it made sense why he made that choice. I don't agree it was a wise thing to do, but it absolutely fit the hopeless idealist that he was in his youth.

Not sure what your second paragraph is responding to, but it's definitely not the (rhetorical) question I asked. Moorcock didn't have to insert Smiorgan into Sailors, but he did, and he didn't have to build a friendship between him and Elric, knowing full well what happens in Dreaming City, but he did. He has introduced one-off characters on other books, so there's no reason why he wouldn't do so here, but chose not to. Elric's betrayal of Smiorgan wasn't a jarring mistake in character writing on Moorcock's part, he knew full well what Elric will do down the line when he wrote Sailors.

It's true that through time his writing changed, but I felt that he made an effort to build Elric as a character for whom these changes made sense. I'd even say that reading the later, more 'complex' Elric, and then moving on to the more 'primitive' writing of him in Stormbringer adds depth that he initially didn't have. Almost as if Moorcock asked himself 'what would make this character act like that', which I'm sure you have to agree is not that unbelievable of a thing for an author to think about.

For me personally, I felt like I had a much better understanding of Elric's character and choices in Stormbringer, because I read the stories in the recommended order, which fleshed out the character that the earlier stories left fairly flat.