Changing the processor architecture over for the first time was going to be a massive undertaking (I'm sure there are still folks there who have nightmares about universal binaries from '06). They had no way to run a wide public beta of the hardware before releasing, so had to play it as safe as possible.
The only sane way to migrate something so fundamental is to change absolutely nothing besides the processor, so that you have a side-by-side comparison between the previous generation and the new one out in the wild to debug problems that come up. If they had added [Face ID / a touchscreen / new mechanics for the keyboard] they'd need to debug whether those changes were causing the bugs rather than the M1 changes.
That's why I've fought myself to hold of - I'd expect the next MBP to be a fundamental redesign.
I can live without a touchscreen, but please just give me a Face ID laptop Apple.