@headplastic Not sure of this helps, but when you say "IDM as popular music" I associated this immediately with the crossovers happening roughly 10 years ago in hip hop/r&b. Where artists sampled other underground artists (Kanye sampling Aphex). Timbaland and co were borrowing beats and techniques from all over the place and applying it to popular music. Going back further, to the nineties and early 2000, you have crossover stuff like Bjork and Madonna even. I'd mention the trip hop stuff also. Like Massive Attack and Portishead, and the likes. More recently John Frusciante moving over from rock towards IDM is also interesting. And I want to put Trent Reznor there as well. Also stuff like Underworld, Prodigy, Chemical Brothers, Daft Punk. It's not really IDM anymore, I guess, but it's typically electronic music moving into the domain of popular music.
That's what I personally consider as IDM leaking over to "popular music". It's all about crossing over certain barriers. Either by sampling underground stuff directly. By being influenced. Or by Aphex Twin and the likes being played on MTV in the nineties.
My guess is that currently, you could argue that music in the charts is influenced in terms of the production techniques. Music nowadays tends to be built on a grid using software. This has been heavily explored in IDM space, I'd argue. Although not uniquely.
Side note: to me, as a thesis this appears to be a bit too broad a subject though. I'd put more focus on a single artist and the connection with popular music. Kraftwerk would be a good example, I guess.