Kenneth Chang

Feller book: "[In 1940s] few mathematicians outside the USSR recognized probability as a legitimate branch of math" And Doob "Feller & 20th century probability" seems to make a handful of references to probability and 'respectable established topics' being at odds in 30s & 40s ?

yes, this is another great example of mathematicians retrospectively claiming probability was a backwater in order to exaggerate the novelty of their current work; may even be a source of Labourie's impression.

the basic fallacy is to claim that because the people/topics/methods have changed a lot over the last 25 years, therefore whatever was being done 25 years ago was insignificant

Labourie did not say the previous work was insignificant. Sorry if I did not portray his words clearly enough, but he did not say that, full stop.

insignificant in the fairly literal sense of "most ... did not think much" of it, which was the line from the article. even with 280 characters one resorts to shorthands like this

Ok, blame me. He meant the hierarchy of the “difficulty” or prestige of the different areas, e.g. theoretical particle physicists think they do the most pure physics, followed by condensed matter, etc. That doesn’t imply solid state physics (and all the tech) is insignificant.

And thus for many of the top people in the field, these other areas are not worth their personal time and attention. Many theoretical physicists have this view even though the March APS meeting is huge.

I don't think mathematicians generally thought what Kolmogorov, Levy, Feller, Tukey, etc. were doing was not difficult or worth attention relative to work in other fields, at least judging by their recognitions, involvement in organisations, etc.