What stands out to me about the people in the article is that they don't seem to be poor in the conventional sense. The woman who sold her 5 bedroom / 3 bathroom house and the guy getting 3k/month in pensions.

I don't hail from the US but wouldn't it be possible for people like that to move to one of the low cost states and rent a modest apartment? I have a friend in Tulsa and I think he pays something like 750 bucks per month for what looked like a pretty nice flat, seems possibly cheaper than this:

"When the family is unable to afford a spot at a campground, which can cost $25 to $45 a night[...]"

You may be right. I grew up in the Midwaste but when I was living in California I met a number of native Californians that I am sure would never consider heading to the flyover belt of America. Rightly or wrongly I think they have stereotypes about what it's like to live here.

(And to be sure, the weather is not what they are used to.)

It's because they're not looking for a place just to live, they want a place where they want to live. Otherwise RVs would be parked all over America, instead of just in downtowns and other urban areas. Everyone wants to live in the Noe Valley and walk to the Whole Foods, but space, and supply and demand make that simply impossible without absolute government control of housing.