They say that to avoid emergency intubation early intubation was preferred.

There are lots of ways to avoid emergency intubation. Early intubation is only one of them, and it was preferred because it avoided exposing staff to risk of infection. I've given you multiple sources that explicitly say that protecting staff was a major reason to use early intubation rather than other, non-invasive forms of ventilation. Why do you still deny it? You're coming across as a Denialist here. Deny deny deny deny no matter the evidence given. (Reminds me of my time arguing with Creationists in the 1990s.)

Your claims that inutbation was not believed to be medically necessary,

I never said that intubation was never necessary.

I have repeatedly made it clear that the problem was the over-use of intubation, as a first rather than last resort, and often in association with excessive oxygen pressure and too strong sedatives.

I'm sure that most of the front-line staff at the time convinced themselves that it was justified. They weren't intubating people for fun. Others went along with the practice because they were following the protocols that the hospital required them to follow. At least one doctor quit over the issue. An early whistleblower, Dr Cameron Kyle-Sidell was put on leave by his hospital for challenging their protocols and transferred to another department.

The protocols were coming fro Chinese doctors who had done this in Wuhan and said it was necessary. And there are studies that suggest that other methods of supplemental oxygen might spread the virus, which was a legitimate concern. And while all this was going on, the media was spreading horror stories about Covid -- many of them hoaxes -- and people were panicking. Medical staff included, especially since they couldn't get enough PPE in the early months. Remember the nurses covering themselves with rubbish bags as improvised PPE?

• You had the media severely exaggerating the risks of Covid (people dropping dead in the street all over Wuhan! the government sealing people in their homes! so many dead in Italy that the army had to be called in take away the bodies!);
• highly stressed medical staff who couldn't get enough PPE and were dealing with a new disease they had never dealt with before;
• professional medical associations were emphasising early intubation and avoidance of NIV as a way to protect the medical staff;
• and early protocols, run by inflexible hospital administrators who often resisted any change to the protocol even as patients were dying.

The early protocols were based on patients with ARDS -- but Covid patients mostly didn't have ARDS and didn't respond like ARDS patients. The tretment was all wrong, and doctors would have seen that it was all wrong if only they had looked at the patients' symptoms instead of just running the protocol "positive Covid test + low SpO2 therefore intubation".

include your belief that 30% oxygenation is safe ... Much greater than the 30% you claim is safe.

And again you are grossly mischaracterising my position. You know damn well I never said 30% was safe.

First you criticise me for saying that organ damage doesn't start until 40% blood oxygen saturation, and death at 20%, now you accuse me of saying that 30% is safe. Seriously dude?

That paper has NIV indicated when Sa)2 < 93%.

Sure, in the same way that blood pressure meds are indicated if you have a B.P. of 140/90, you don't rush them into open heart surgery.

You know that Non-Invasive Ventilation isn't intubation? That's my point, for the upteenth time -- there were non-invasive, less dangerous treatments which the hospitals failed to do in order to protect the staff. It isn't that they had no choices except "intubation" or "let the patient die", they intentionally picked intubation over the other safer choices (non-invasive ventilation, prone positioning) to protect staff.

And when they did intubate, they often used too high pressure, or too many overly powerful drugs to keep the patient sedated.

Of course doctors should prefer to get oxygenation to normal levels, if possible. For many people with chronic illnesses, its not possible, and doctors are satisfied with just getting it to the high 80s or low 90s. But the point is that you don't rush somebody into mechanical ventilation with intubation just because they have an SpO2 of 90% or 80% or even 70% when they show no sign of ARDS.

Even a 70% SpO2 level in the absence of respiratory distress is not "oh my gawd, call Code Blue, get the crash cart, they're about to die!" situation. Yet again I refer you to the case study of the woman with an SpO2 of 70% who had no respiratory distress, and was treated with non-invasive supplemental oxygen to get back to the mid 80s and eventually, after spending 30 days fluctuating between about 85-90%, eventually made a full recovery from Covid.

"A study reported that NIV was indicated in ALI and early ARDS when desaturation (SaO2 < 93%) occurred despite oxygen supplementation (> 3–5 L/m), with persistent tachypnoea (≥ 30/min) and progressive deterioration on CXR. 11 Intubation could be avoided in up to two‐thirds of cases in a Hong Kong series

Right, now you get it: Intubation could be avoided just as it says.

The usual contraindications to NIV apply

Sure.