LRT: This is the one topic I know at least half a fact about.
Today marks 120 years since the JP government ordering that primary school textbooks should only use one type of hiragana character per syllable from then on.
But this is only about textbooks - what about other books?

Turns out that the use of "hentaigana" (non-standard kana) dramatically decreased in movable type printed books around 1890 - ten years prior to the government's order.
I did a paper about this - it's in Japanese but it has nice charts on p. 29: http://www.lib.kobe-u.ac.jp/repository/81011665.pdf

Fig 1: Woodblock-printed books (X axis is "year of publishing (in the Meiji period)," Y axis is "number of different hiragana characters used in that book")
Woodblock books have a wide spread. Fewer woodblock books after 1882 so I stopped collecting data from there on.

Fig 2: Movable type books (same axes as fig 1)
There are outliers, but you can see a clear downward slope. There is a clear-ish cutoff at M. 21 (1888) where most books have under 65 types of hiragana characters (remember that there are 48 hiragana "sounds")

I think it is rare for "top-down" approaches to succeed in terms of language change. The standardization of hiragana in textbooks was not actively trying to restrict hentaigana use; it was following common practice that was already present in publishing at the time.

In a later study I focused on books from the same publisher in around 1890 - I found that the use of hentaigana differed depending on the printer. There is clearly something going on at type foundries and printing companies around this time, but I was unable to identify details.

It is great that these books list the person and company who printed them - this was mandated for books published in 1888 and onward in Japan. Sadly, older books rarely list the printer, making it harder to further investigate the relationship between printer and hentaigana usage