Are kids playing with toys they know nothing about?.
This is definitely something that happens from time to time. Apparently the Ohranger toys were just considered extremely fun and well-made toys, so you did have kids buying the whole line who didn't watch the show regularly. I've heard this disconnect between toy success and show success was one of the major factors that lead to Sentai's time slot change a few years later.
This isn't something that happens often in the North American toy market, since the market here has shrunk to the point where most kids have little interest in toys that aren't part of major brands. Power Rangers was one of the big exceptions to this, selling steadily even when the TV incarnation was being buried in graveyard slots.
I imagine kids who played with Ohranger toys knew at least the basics of the premise, if only from the box packaging. Many of them probably caught a handful of episodes or saw the Ohrangers in stage shows or rented their video tapes. I imagine some kids may have enjoyed making up their own Ohranger story to play with the toys more than watching Toei's, though.