I realize this is something of a counter-factual question, but I think it might be answerable to some extent. Various groups of Polynesian peoples settled very nearly ever single island group in the Pacific that has a supply of fresh water, which suggests they explored all the ones that don't. Given this, why was the Galapagos never settled by ocean-going peoples? Is the distance from any other island groups simply too great?
Not only is the distance very great, but both the water currents and predominant winds near the Galapagos are from the Americas. So there isn't a good way to approach from the west. Basically everything would be pushing a Polynesian away from the Galapagos.
Of course this wouldn't be an absolute bar, the Polynesians were good sailors and could tack against the wind. It would make these distant islands even more distant.
It's not too far away from several of the places in South/Central America where Polynesians likely did make contact, so it's possible they could have stopped by during one of the voyages that saw sweet potatoes and coconuts and maybe chickens exchanged- but there is certainly no direct evidence that they did in fact stop there.
As to why they might not settle the islands, even if they did stop there, it is my understanding that the Galapagos doesn't have flowing or easily accessible fresh water? Perhaps I am wrong, but without available fresh water, transforming the islands into habitable spaces would be very difficult.
The island, as already mentioned, is against the wind, so sailing there would have been more challenging- though as I have posted elsewhere, sailing against the wind is actually pretty beneficial, it makes it a whole lot easier to get home if something goes wrong. Assuming navigators had stopped on the island and noted its celestial location, they could certainly have come back- but as I doubt the islands looked terribly promising, I have to imagine they probably didn't think it worth the resources.
Distance definitely plays a role- other islands with limited resources, like the Tuamotu archipelago- or any of the coral atolls- would have been peopled over generations and slowly transformed from seasonal fishing grounds to permanent settlements. It took more than a few years to really establish the necessary biota on any given island- so it helps immensely if you already have a solid base no more than a week's sail away- and the Galapagos would have been probably about a month away.