So the question is

Why was the PM admitted to an NHS run ICU, which was seemingly 'overrun', at the time when his treatment could have been administered in a regular ward or possibly even at home?

I think the answer is propaganda -

'how do you get get an incompetent PM to u-turn on some of his blurted out and ill conceived comments and at the same time time scare the gullible into thinking this pandemic is a bigger issue than it really is Matt'?

'I know Dom, let's pretend Boris has Covid so bad that he needs admitted to ICU. The mugs will have visions of him in an induced coma and on a ventilator like the genuine patients so will take pity on him when in reality he'll be sitting in that bed reading whilst others die around him. We can then paint him as a stoic advocate of all the restrictions we want to impose on people and can claim he knows how bad it can be because he's been there'.

'Brilliant Matt, and down the line when asked about it we'll just lie because at least that's something we can do well'.

'Excellent Dom, just you go and self isolate up in Durham for now, I'll take care of it'.

'Great idea Matt, I have a castle on my to visit list, I'll get a trip there while I'm away'.