Most of those 160 pages, is repetitive mish mash of various historical research (many of questionable quality) on typeface readability loosely grouped by certain themes retold in a way that makes it even less clear about their results, quality and whether testing conditions are useful for making any good conclusions. Little value in reading it all unless you follow references and read what the quoted research actually did and said. The chapters have different thematic, but content and conclusions are very samey -> a bunch of questionable research and research which was inconclusive or didn't observe significant overall advantage of serif vs sans serif.

As for where it came from to me it very much feels like the defense of serif typefaces is largely typographers defending existence of their craft and people talking past each other with overgeneralized claims. There is definitely value in the art and craft of typography and I respect that. It would be too bland if everything used plain sans serif fonts that barely differ from each other, and you can definitely mess up typography making text hard to read when done badly. But I also believe that there is plenty of things based on traditions and "everyone knows x because that's how we have always done it".

As for sans serif for screens the obvious reason and also thing that comes up multiple times is low resolution text. At certain resolution there are simply not enough pixels for serifs. The author of paper suggest that with modern high resolution screens this argument doesn't stand. My personal opinion is that it's not a big issue at sufficiently high text size. But even on somewhat modern 2560x1440 screen I can find plenty of UI elements that have only 7-8 pixels high labels. Not everyone is using retina displays and not everything is long format text. Screen resolutions have increased, but so have information density compared to early computer screens, although there is recent trend of simplifying UI to the point of dumbing it down and adding excessive padding all over the place. There are other screens beside computers and mobile phones, many of them not very high resolution even by standards of early computer screens. It doesn't make sense to put high resolution screen and Linux computer in every little thing. Problem is made worse by lack of antialised text sometimes due to screen, sometimes MCU memory and compute limitations. You are probably not going to have modern font rendering stack on something like black and white washing machine screen, gas station pump or thermostat The research multiple times mentioned stuff like low resolution, but it hardly ever quoted hard numbers in a meaningful way. How many pixels a typeface needs to be comfortably represent serif? How many arcseconds? Surely there must be research related to that one. This might be part of problem for some comparative research - can't compare readability of serif/sans serif if there is no serif typeface at those resolution. Stuff like point 10 or point 12 without additional details is meaningless.

Some personal anecdote -> text antialising has huge effect. Made a sample text of serif and sans serif font and zoomed out to the point where lower case letters are ~6px high. I wouldn't expect there to be enough resolution for serif but you can perceive surprising amount of detail in letter shapes. Zoomed in on screenshot it's a blurry mess, but at normal zoom level the serif letters are fine. It's readable but wouldn't consider either of 2 comfortable. When scaled up to 8px both pieces were still harder to read than same height text in UI labels. Why is that? Why is one identical height sans serif text much more readable than other? Are UI labels better pixel aligned? Is it due to subpixel antialising? That's on a 90deg rotated screen, is subpixel antialising even working properly there?

Just for fun switch OS UI font to serif. Due to font sizing inconsistency it ended up being 1 pixel shorter (7px) than same size default UI font. Can those even be considered serifs when they are hardly a pixel each? It felt weird, nowhere near as bad I expected, but still weird.