Yes they knew Apple maps was bad and not up to standard yet, but they didn't really have any other choice.
Quite plausibly they just didn't realize how rocky the start would be, or perhaps they valued that immediate strategic autonomy more in the short-term that we think, and willingly chose to take the hit to their reputation rather than wait.
Regardless, they had choices.
> They could have launched a submarine non-apple-branded product to test the waters.
This is a great idea. Are there any past Apple (or non-Apple) examples of this product release strategy?