It's interesting that this article doesn't touch on this aspect of the situation at all, but when reading about Mochizuki's proof in the past it was presented as clear that proving the ABC conjecture was one application of a new general theory—not that all of Mochizuki's innovations are tied specifically to that problem.
I was given to understand that his work was more like Grothendieck's, where he's developing this entirely new, super general system. But you can imagine if Grothendieck for example had done all of his work for years and years in isolation and then presented Schemes, Topoi, and Motives to everyone all at once, using them in combination to prove something familiar, and expecting other mathematicians to just learn and understand them all in order to verify a single proof.
I think in that case, folks would not have been immediately so interested in the new constructions Grothendieck had come up, viewing it initially as mountains of unnecessarily alien concepts built up just to give other mathematicians a hard time ;)
(Not to identify the two mathematicians overly—I'm not sure how appropriate that really is—but I remember that being my impression when first digging into Mochizuki's work, and I haven't seen it mentioned here yet.)