Thanks for that really interesting summary!

Regarding backwards compatibility, is this basically that certain companies developed new products so quickly that there was no point (or value) to supporting old hardware (for the company, or desired by users)?

And therefore delay + overheads of waiting for compatible new CPUs was worse than the value of what they did release each time? Plus the generally worse heat/power utilizing designs?

It is of course a general stereotype in that its useful for prediction but its not as solid as, say, the law of gravity, but ARM comes from a software as a project world where you write the code for a specific piece of hardware with a defined and short production life, whereas Intel desktop PC comes from a software as a product world where you expect your word processor to keep working even if you replace your motherboard or swap in a faster CPU. One has a world of permanently sealed cases and firmware thats never updated (with unfortunate security results) whereas the other at least in theory has user-serviceable parts inside a screwed together case. Ironically that sounds a lot like MAC vs PC so it makes sense that MAC would go ARM.