[ma70]

Interesting that so much water could leak in from a failed speaker seal. I wonder, did you also check the drain holes in the bottom of the door?

As you've noted, the window "seals" are never going to provide a perfect solution & the inside of the door is designed to tolerate water ingress and direct it to the bottom of the door shell from where it's meant to drain, hence the membrane layer between the door shell and door card to keep moisture away from the fibre board of the door card.

With that much water (unless the weather has been really serious) I'd expect to find the drain holes at least partially blocked.