Why would SquareEnix create FFVII Advent Children movie?

Ok so, its a long time since it was out and heck, they even released advent children complete last year of the year before. when it first came out, i was like, cool they are all cgi and very realistic with over the tops moves which is freakin sick. lately, i just had a thought and remembered this final fantasy series but something's bothering me, and im talking about the movie. why would square enix create this movie for? i dont see the sense of the major plot of the movie. its just these three guys that are Sephiroth's other sides which appeared out of no where and when they get a hold of jenova, sephiroth came back and later dies again. whats the significance? i dont see the point as a continuation to the series. things appear out of no where without explanation, no major twist to the series like a new enemy or something, they are just playing around with the story and recycling on what it has. where did those three dudes came from? where cloud gets his new sword? who is this denzel which appeared out of no where and plays no major role? is it just a test subject for square enix on cgi technology for future games? or they just wanna earn some extra income?