The words "Then your son will be King" sounded too easy coming from Aprophil's mouth but Katarina was too experienced to believe that a kingdom as huge as Prophis can be taken that easily. Once the capital is sacked and a new King is crowned, then other cities will follow but Raven wasn't a small town or a city like Whitebridge to say it may fall within a day.
Raven was twice the size of Whitebridge, and twice size of King's City and thrice size of Claydall. During her husband's reign, Katarina did ask Castellan why didn't he rule from Raven ─ the biggest of all cities in Prophis, not to say the most profited one and it was always hot in Raven compared to King's City which snowed throughout the year.