They didn't know what to do with a plot that didn't have Seven in the lead--and even though the finale was obviously coming up that whole season, they couldn't decide who would die (because that is the new way to end all Trek series--hence Trip's death in the TNG conclusion of ENT).
At first, it was going to be Seven, for sure, but what a downer that would be. So, instead, they brought back Admiral Janeway for the Red Shirt Supreme--assimilated and killed, not a downer at all because we still have the captain carrying on for her.
However, Seven couldn't just sit around filing her nails, so what to do? Pair her up with Chuckles for some much-needed "romantic" action in what has to be one of the lamest B plots in history. Don't bother with any sort of build up for them as a couple or worry about a complete lack of previous chemistry between the two characters. The fact that it is the fourth date should erase four years of lukewarm friendship. Ignore the touching and very effective "Human Error" that finally made Seven a character one could feel sorry for because certain aspects of humanity were forever beyond her reach.
It's the finale, so who cares about continuity or whether this "romance" would screw up two characters as we knew them? The producers had moved on to a better, edgier ENT that would make VOY look like slop.