[Marsh.]

DS poster got it spot on...

Since the series moved to Channel 5, Channel 5 made a big point about no longer needing the old Channel 4 viewers. They were old, they didn't know how to use social media, in fact they were an irritant they'd rather get rid of. I think that what they're trying to tell you is that if you're a BB viewer who used to watch it on Channel 4, then you're no good, and you probably stink a little bit like poo too.
Because people have to 'move on' and make way for this brand new modern breed of viewer which Channel 5 have in mind. A new, fresh, dynamic, computer literate viewer. That's the demographic they're now going for, and who the advertisers want to sell their wares to.

And in Channel 5's imagination, this brand new modern BB viewer they have conjured up in their mind, is fickle, only wants the arguing, likes TOWIE, likes 'I'm a Celebrity', it has a short attention span, so wants instant gratification.
It's all there on a spreadsheet, the marketing people and analytic TV data boffins have told them so.

So year on year they decimate their audience. Out with the old, bring in the new. Short attention spans however need constant feeding. When they get bored they're going to go and move on to some other shiny thing which has caught their attention.
So we end up in a situation where many of the old CH4 viewers leave, and any new viewers probably come and go, but they're not enough to keep up with the exodus of viewers they're experiencing at the same time.

So they try and find out what the problem is and refer to the business spreadsheet of their ideal demographic of this new Channel 5 BB viewer that they're trying to target,..... and then come to the horrific realisation that Oh no, This perfect Channel 5 demographic of the ideal BB viewer they want may not have actually existed in the first place.
Or at the very least, they failed to realise the extent to which that very type of viewer they were aiming to catch isn't going to be a loyal viewer who will hang around for long.

So now if they try to revert back to an earlier model of BB they have the problem they have made for themselves where they have alienated so many of the old viewers they can't get enough of them back to watch the show. And all they are left with are a small audience who come and go but don't really hang around for long and just make a fleeting visit if something catches their attention.

Whatever they do now can't be a quick fix. They're going to need to build up from scratch and build up a loyal fanbase again over time. Which may take a very long time.
Rather than being very short-termist and trying to cater to a certain type of viewer who has a very short attention span and needs instant gratification, they should perhaps take a more long term view of the show and re-teach viewers how to get used to enjoying a more involving show which understands pacing, buildup of drama, and which viewers find interesting in terms of how the word 'interesting' used to be defined in the dictionary. A person who likes to scream and shout and thrives on conflict and histrionic drama is not the same thing as an 'interesting' housemate.

When things get bad enough they are left with two options. Try and build from the ground up, which may take a while for the viewership to grow, or simply throw the show into the bin and don't even bother with it anymore.