^^^That's an awful teaser. If I was new to Dr Who at the time, that would have turned me off of it completely.
Perhaps, but remember it was 16 years (except for 1 TV Movie) since DW had last been on screens. So all those children who watched DW as akid were now adults. So you would have a certain nostalgia factor of those who watched it asa kid tuning in now with their kids.
As for first episode "Rose" these were it's figures
44.3% audiance share
3rd most watched BBC One programme of the week
7th Most watched show in the UK that week