If you want to know how inevitable post-anime could be, look no further than post-punk’s history. Post-punk practically came after punk rock and adapts punk rock to much wider influences. Especially now that punk rock ceased to exist in its current form at that time. Public Image Limited came after Sex Pistols, The Cure went from a straightforward punk band to one of the most accessible Goth bands to date and even The Clash dabbled in reggae soon after.
Especially once the 1980s dawned. Logically and parsimoniously, punk rock is directly based on glam rock in the sense of marrying trashy sounds to equally ironic trashy fashion sense. (Malcolm McLaren managed the New York Dolls before moving onto the Sex Pistols, Mick Jones admitted to being influenced by David Bowie and Sid Vicious modelled his hair after his.) Maybe not always nor consistently the case.
If I’m not mistaken, there were already mangaka influenced by western movies and comics before I was born let alone come to recognise these franchises. What post-anime would do’s to take in Western influences as substitutes/replacements after anime died. Pretty much what post-punk musicians did.