I can only speak for SFDC, but I believe Marketo relies on SFDC lead assignment rules to dole out the assignment. You can, however, also specify an owner in Marketo.
I believe the only way to assign owners during list import is to create a smart campaign with a "Sync lead to SFDC" flow with a bunch of conditional criteria. See below. Instead of using Last Name like I did, you can also create a smartlist for each if you want to use both first and last name, and then just specify the smartlist in the flow rule.