RE: Ahsoka series (see detaills)

How come the Night sisters and Thrawn couldnt detect Ezra Bridger on the carrier/space craft ? Or did they hence Thrawn has a plan behind it ?

I think they just didn’t focus on finding him

I mean, Ezra stole an entire ship so there's no way they wouldn't have known, but that's small fries overall. Thrawn accomplished his mission. He returned to the main galaxy as heir to the Empire and returned the Nightsisters and their cargo back to Dathomir.