Mostly agree with all you have to say minus the reference as Steve carrell being a safe, reliable pick at the time period. Being on the daily show is a great metric for a casting director as far as quality goes but in reality he had close to zero exposure and public recognition before the office.
That fact is supported by how bad the first season of the US office did ratings wise. People warmed up to it quickly thanks to the quality of writing, but the showrunners and producers clearly didn't feel confident in the future success of Steve carrell as a leading star or they wouldn't have ordered he get hair plugs to make him more look more likable.
Lastly, there is something to be said, at least regarding comedy, about differences in taste between cultures. British and US comedy have often been quite different over the last 70 years and is evident in the stylistic differences between the british and us versions of the office in season 1.