Did they pay you at all? If the contract was never really signed then basically everything they were telling you were just suggestions. It sucks, but honestly, it's really common for an editor to back out before you sign a project. It's not a reflection of you or your work, it's just that it probably didn't jive with their brand. Or maybe it did at first but they changed their branding? Who the hell knows, it's not worth wondering about. Finding illustration work is like dating in that way. Thing is though, you want to be paid for your time, so that sucks that they led you on for so long. Usually an editor won't do that. Usually they're very clear about "these are suggestions you can take with a grain of salt and we aren't committing to you yet." The fact that they didn't already know the details about the contract right away was a pretty flighty move on their part and they clearly lack some communication here.
Like once I was making a kid's book and I was sending it around to slush piles and I heard back from an editor, who gave me a really wonderful critique but basically needed me to rewrite every facet of the book except for the idea. They were all "let me know if you do" but they knew and I knew that it wasn't going to happen. It was like 100+ hours of work. No contracts were signed, they were just giving suggestions to let me know what their company likes to see. So, now if I make a different book that I'm like "youknow this is more in line with what that editor needs" then I can send it to them. Its not a negative thing that it didn't work out--it's not that my work was bad, it just wasn't what they needed at the time. It sucks that I got my hopes up for a while, but over time I've decided it was honestly for the best.
I know that it super, super sucks when things get rejected, although it looks like this particular editor might just show up again out of the blue months from now (this guy seems kind of random) but try not to take it out on your work or your talent. It's not your work's fault. There's so many reasons they might back out--money issues, branding issues, maybe they changed some people in their workforce, maybe they just got a lot of work backed up and don't have time to release new projects anymore (publishers don't actually publish very many books a year)? Who the hell knows. All in all, your comic is still yours to self publish all you want, in the style it's meant to be, and in a way that truly clicks with you, and I hope you can come back to it some day.