I still think they thought they'd be the popular pair overshadowing W&K. Adoring crowds, making money, leaving the dull work to the 'work horses' in the RF.
Clearly that was the plan - Sussex Royal website all ready to go and pump out PR about how wonderfully philanthropic they are, bla bla bla. Pity they fucked it all up by not asking permission and just assuming it would all be okay with Her Maj.
They were clearly receiving advice and encouragement from across the Atlantic from Meghan's PR firm and her celeb pals saying things like: 'Come to the US, we love the RF over here, can you imagine if you're based over here? You'll be the American outpost of the RF. Everyone will love you!'. They believed all the smoke that was being blown up their arses, because they wanted to. In their heads, they were the cool, modern stars of the RF, everyone else was a stuffy frump and if they could just be freed from the shackles and the limitations of royal hierarchy, they'd be the stars of their very own show ...