Who exactly is the target audience here?

EVERYONE, obviously

Then they all fuck Elmo!

It’s hard to say nowadays what parent will or won’t let their kids see. However even if most kids haven’t seen GOT, they are likely aware of it, and even if they don’t know who the characters are or the relationships between them- it’s a castle, there’s a message about respect- you do t actually NEED to know it’s even about GOT to get the overall message. If you’re an adult who’s kid watches Sesame Street or an adult who watched or is aware of the Sesame Street brand though- the added nuance of knowing the characters relationship to each other and actions is an Easter egg bonus. So- really it’s for most all audiences but like many Pixar or other works is aimed at kids with a nod to adults so that it isn’t torture like Dora the Explorer to watch.