I wouldn't credit or blame academia for the initial spread, I think it's more about the set of situations described by dot and boles in their comments, especially the increasingly bonkers cognitive dissonance that was required to hold on to Soviet-style communism, and the appeal of national liberation style politics to provide an analysis of race politics in the US that other radical varieties lacked or seemed to lack.
But really the question of the initial spread and foothold is probably less important than the question of how it's spread so insidiously, how many people who profess to be anarchists or consider themselves just plain radical or leftist, are riffing so heavily off of Maoism. And this, yes, has a lot to do, in my opinion, with academia, as well as some other factors I'll try to cover.
So yeah, academia. What happened to all those radicals you hear about from the 60s? Some were killed, some were imprisoned, some went into exile. A few are living out their days on a commune somewhere. But they went into the universities in droves. I have no citation for this, but to me it seems just a fact. And a big part of the reason to go into teaching is to have a formative effect on young people. And sure, some will have drifted away from that mission, but you can still spread ideas unintentionally and unconsciously as easily or more easily than spreading them on purpose.
The next thing to consider is that it's a big thing for Maoists not let on that they are Maoists except in "cadre" or insider situations. And I don't mean this like how many anarchists won't let their bosses or coworkers know that they're anarchist, or the kids they teach or those kids' parents. I mean that more often than not, died-in-the-wool Maoists will be totally outright with some Maoist political line but will deliberately conceal where it's coming from. I have seen this with Maoist groups where I live, and every Maoist I've ever interacted with, which is quite a few, unfortunately. And I'm not talking about the RCP here, they are just the tip of the iceberg and a particularly silly one at that.
It gets trickier because most Maoists are into anti-authoritarianism -- though this term has a particular meaning in Maoism that is not particularly anarchist -- so they are able to go around masquerading as anarchist-adjacent even though they have a deep and abiding love for the dictatorship of the proletariat. Really weird situation. Where I live, there was an armed group back in the day that was made up of full-on Maoists working together with anarchists.
And that's just the Maoists who know they are Maoists. Then you start getting into all the people who don't think they are Maoists, but have absorbed a whole ton of their ideas about anti-oppression, identity politics, imperialism, capitalism, colonialism, race, and so on, from Maoism. It's like fish not knowing what water is.
I think developing a good sense of what to look out for is a good survival strategy, at least if you intend to be an anarchist in certain cultural conditions. Unfortunately I don't know of a good historical examination of this question -- though I'm sure some of the stuff linked in the comments is worth checking out, and I know someone who has a draft of a book or long essay on the topic. But do check out Manual for Revolutionary Leaders -- it would be a perfect start for calibrating your bullshit detector. I would recommend reading between the lines of the history books and of what's out there in the world around you, reading with your guard up. It's extremely common in universities and colleges, in leftist publishing, in activist circles / community organizing world, and whatever parts of the internet the tumblr kids are moving toward these days. Make a decoder ring with Maoist code words and their translations. It would be interesting to see some kind of working group form around this question and put out a historical narrative and/or a how-to manual.