I am confused by how the objective worth of CS theory research is assessed.
In the last year, I had been working on formalizing some tasks from a different research field in cs theoretic terms, i.e. providing proper definitions, proving bounds etc. In the end, I came up with two proper theorems that are relevant in my research field. Let's call them $A$ and $B$.
That Theorem $A$ should hold is quite intuitive, yet my rigorous proof involves several presumably non-trivial steps. Theorem $B$ is relevant for the field, but follows trivially from the definitions.
When I presented my preliminary results to some acquaintances who were knowledgeable in CS theory, they praised result $A$ and paid little attention to $B$, making the comment But this is trivial. In fact, I had the impression that they didn't read much besides definitions, lemmas, theorems and proofs.
Later, I distilled $A$ and $B$ into two seperate papers, because they were quite different. I submitted both paper to the same journal, and the paper about $A$ was quickly accepted, whereas the paper about $B$ was rejected with the comment All described results follow trivially from definition 2.
So, my question is the following: Why does it matter in CS theory how difficult the proof of a theorem is? As a domain expert, I can say that $A$ and $B$ are equally relevant to my field. Of course, $B$ follows trivially from the definitions, and most theorists could have quickly solved that -- but as far as I know, nobody did. Arguably, the main contribution for $B$ was the definition that implied the theorem--which, by the way, was quite hard to come up with--but nobody seemed to care about that.