All lowercase signals casual aloofness; it says the situation doesn't meet your bar for formality. It's like Zuckerberg wearing a hoodie when meeting with Wall Street types.

It is done to signal solidarity with sama.

Some people wear flags as lapel pins to show their solidarity with a cause, some wave flags in the street, some post black images on social media.

Others remove the captials and punctuation from auto correct and post in lowercase.

People are reading way too much into this, some people just prefer the look of all-lowercase. It's not like this is some super-unique choice to Sam / OAI, it's all over the internet.