Is your argument that the 1 employee operated on peer pressure, or the other 999?
Could it possibly be that the majority of OpenAI's workforce sincerely believed a midnight firing of the CEO were counterproductive to their organization's goals?
Doing the math, it is extremely unlikely for a lot of coin flips to skew from the weight of the coin.
To that end, observing unanimous behavior may imply some bias.
Here, it could be people fearing being a part of the minority. The minority are trivially identifiable, since the majority signed their names on a document.
I agree in your stance that a majority of the workforce disagreed with the way things were handled, but that proportion is likely a subset of the proportion who signed their names on the document, for the reasons stated above.
It's almost certain that all employees did not behave the same way for the exact same reasons. And I don't see anyone making an argument about what the exact numbers are, nor does it really matter. Just that some portion of employees were swayed by pressure once the letter reached some critical signing mass.
What makes this "likely"?
Or is this just pure conjecture?