It could happen. But if Apple leaves Europe, there will be suddenly lot of developers, who will have no motivation anymore to release anything for Apple and all applications will be suddenly for Android only.
Do you want to use our product? Well buy some Android phone instead of your toy phone. Does not look good in a long term.
For me they can happily leave if they feel like it.
We would get back to the 1980 - 2000's period, where Apple hardware on Europe was mostly seen on computer magazines, while we played with Atari, Amiga, Archimedes, PC, MSX, ZX Spectrum and C64.
The examples you gave were all 80s systems, even in back waters like NZ :D
By the end of the 80s even the big non-MS players were largely irrelevant, and the entirety of the second half the 1980-2000 was MS. If you're talking about hobbyist/minor OS's, those are more available today than any time previously, depending on your definitions I'd argue hobbyist hardware is more available as well.
I'm not sure how Apple existing or not in the EU impacts that availability, but I haven't lived in the EU in almost 30 years and where I did live while there decided not to be there either, only for stupid reasons rather than visa limits :D
"Existing" doesn't mean surviving in any meaningful sense, and if that is the argument you are taking, then the existence of apple in the EU definitionally did not impact that world either.
That's the later point I made: Apple existing does not, and did not, stop any of what you're saying you want from existing, and it didn't make it any less relevant either.
You're either talking about existence in the hobbyist/enthusiast sense, in which case apple's existence or not changes nothing, or you're talking about existence in the practical real world use sense in which basically no one other than MS was relevant for more than 50% of your stated time period, and even today apple's existence or not doesn't really change anything (if anything the existence of a large enough non-MS platform is what drove the cross platform frameworks like electron - for better or worse - that mean that a bunch of apps that would historically have been windows only are now also available on linux).
Leaving big markets has been done quite a few times. Most obviously when Google left the Chinese search market in 2010, something that conventional wisdom at the time said could never happen due to the sheer size of the market.
> If Apple leave EU then there will be only Android.. It will be a monoculture then..
That would actually be great, because in that case the EU would have ground to impose Google to sell off the Android division (because it'd be a monopoly).
Do you want to use our product? Well buy some Android phone instead of your toy phone. Does not look good in a long term.