The new theory is that they came along the coast. Clovis culture arrived 13-16,000 years ago through corridor in ice sheets. But earlier sites, including these footprints, suggest that people arrived another way. These footprints are 21-23,000 years ago. I don't think there is any evidence how they got there, but the coast is plausible explanation.
There is genetic evidence linking these very old inhabitants to Pacific Islanders of that time and there were more islands at that time because of lower sea levels.
It's really confusing to use the term pacific islanders here. The farthest humans had reached was the Solomon Islands, what we call "near Oceania". The places people think of when they say "Pacific Islands", namely Remote Oceania (Melanesia), Micronesia, and Polynesia were all uninhabited. Those early Papuans weren't especially closely related to the founding populations of the Americas, though they're closer than you might expect from the geographic distance because of the serial founder effect.
Yes, that is a really extreme simplification. There were at least three major groups of early humans around Southeast Asia and the Pacific Islands 20k+ years ago. The main point of interest is that all of these groups were genetically differentiated from the Siberians who migrated along the vicinity of the Alaskan coast later and who left a genetic trace on native populations that is still observable today.
