I very much doubt whether Shearer was offered the job,
like most senior appoinments there was a list of applicants, and a list of people who were invited to apply,
because they were invited to apply people sometimes assume they are being offered the job, which is rarely true.
This lets the club have a look at Shearer, and Shearer have a look at the club, Shearer then makes a decision on whether he wants to take his application further and join the list of applicants being interviewed. As good business practice, and as a matter of common courtesy, it makes good sense to interview all the candidates on any shortlist before making a decision, and this lot are nothing if not professional...........could you imagine if they just said to everyone on the interview list that they'd given the job to the first or second guy they'd interviewed and the rest could just go home. They may have been impressed by the first guy on the list and after say, six of ten applicants have been seen they may regard him as the best SO FAR, but they won't make a decision until all the candidates have been interviewed it would be stupid to do so.
Shearer being as thick as two short hammers, probably thought that because he'd been invited to apply, the job was his if he wanted it.........but he was not the only candidate.