Voltron didn't lead to Power Rangers. That's why it seems weird to you.
Also, you're coloring it with your opinion. Voltron and Power Rangers are exactly alike in quality, from a non-fan perspective. Both have the same plot over and over again, and both have primary colored animal/dinosaur/monster/vehicle robots that turn into a big humanoid combiner.
I first realized Voltron was stupid when there was an episode of some girl whose brother gets turned into a monster and so Voltron kills the monster everyone celebrates except the girl who is screaming and crying the whole time, and I thought "Wow, not only is that unnecessary depressing melodrama, but it also took a concept that could have been different and interesting and did the exact same thing with it." If I'd seen that **** when I was a little kid I probably would have broken all my Voltron toys. It's either terrible writing or excellent marketing. Probably both.
Both of them, and more, come from Japanese shows called Super Sentai. Voltron is just an animated version of the genre. All the fight scenes in Power Rangers look like old quality footage because they are. They are all from the 70's and Japan. Only the out of costume scenes, or scenes with helmets off, are new footage. The 1995 movie was also all new footage.
http://en.wikipedia.org/wiki/Super_Sentai