If Trump wins, and they STILL don't arrest one or both of them, then we'll know either Trump sold the country out, or there actually was no further evidence to begin with

There's still the fallback of "the swamp". There's enough plausibility in the idea that the system is corrupt enough that the arrests wouldn't be made no matter what evidence they have. Trump could sell out or this could be the extent of the evidence, and there might just be enough deniability for it to not stick.