Yes, they are an emergent property any time you have a communication network where people rebroadcast information based on their preference, but restricted to the set of choices they are aware of.
But I believe the exponent of the power curve increases as the amount of resharing goes up. Before social media, you were still limited by what travel books you saw in a store, or where your friends went on vacation, but there was less reverberation and resonance in the network and a relatively flatter power curve.
The interesting observation is that choosing one of these parks consists of just going through a boring large list of parks in a boring old gov website and picking one at random. Whereas going to, say, Yosemite and finding sightseeing places largely involves going to google and/or local tourism guides and funnel the same way as everyone else (resulting in, as one might expect, arriving at spots crowded w/ tourists)
OK, the redwood trees in them might be only 80% as old and tall, the United Nations might not have been founded inside them, and some of them might have only 6 km of trails through the forest rather than 10 km. But many of these places are often nearly deserted, have no entrance fee, are a quicker and less twisty drive from San Francisco, and are incredibly majestic, peaceful, and spectacular.
Meanwhile, Muir Woods had to introduce a rationing and permit system to visit by private car or public bus (https://gomuirwoods.com/), and along the main trail on the valley floor you are basically never out of sight of other visitors during a weekend or holiday.
I've reserved a picnic area inside an ancient redwood grove for an upcoming birthday picnic.
https://www.yelp.com/biz/lake-lagunitas-fairfax
OK, it's definitely no Muir Woods, but it's just 6 km north of Muir Woods and you can reserve the area for a small fee on a weekend during the summertime.
I think the power-law effects you describe have been true of tourism forever. Muir Woods has attracted dramatically more tourists than the MMWD or EBMUD redwood groves for decades. But I also think you're right that the Internet is accelerating them, because you can hear about where to go via discovery mechanisms that so drastically and rapidly reward pre-existing popularity.
(If you live in or visit the Bay Area, check out https://www.marinwater.org/175/Directions-Maps-to-Watershed-... and https://www.ebmud.com/recreation/east-bay/east-bay-trails/ for information about hiking in -- often -- redwood forests owned by municipal water districts in reservoir watersheds, or https://www.marinwater.org/DocumentCenter/View/156/Map_Marin... for a map of all public lands in Marin County.)