Actually, I'd say that the primary thing that drove the relationship, was that in all the time Worf was featured past the death of K'ehleyr, Deanna was the absolute best person to be a mother to his half-human son, being half human herself, & being an expert in psychology & behavioral studies.
In fact, in Parallels, we find out that the alt-universe relationship began around the time of Ethics, when Worf legitimized her status as a post-mortem guardian for Alexander. Even in our prime universe, there's a little growth between them from that point onward, about once per season, in Cost of Living, & Fistful of Datas, & then the actual relationship seeming to develop after the events of Parallels.
Personally, I feel like Worf's relationship with Jadzia was something of a step backward in his evolution as a father... not that it was the only one. Deanna was a much better choice of partner for a family man imho
It not only felt forced, but it felt like a lame concession, & maybe the second weakest character based plot point of the TNG film series, second only to Picard's brother & nephew dying in a fire. Both done for the same reason... it gave them a quick something to be on about. It really was the paltriest of bones to toss us & them imho. I'd say it did more to undermine the long developing individual growth of both characters (Especially Troi) than it did to improve or validate it. It's another step backwards, as a cheap attempt at fan service, & unnecessary, because personally, until that shit reared it's dumb head, I'd mostly forgotten that Will & Deanna were a thing. We'd all moved on, much to the betterment of us all imho. Then when it happened, I was like Aww man... Are you kidding me? Who needed that shit?
