Yeast salt reaction

I make 9kg of bread every weekend (reasons). so when I wake up I start blooming the yeast: 3268gr of water, 109g of sugar, and about 20gr of yeast. I had to leave for something so I came back two hours later, it smelled amazing, next step is to mix in the salt (218gr) and flour (5440gr) , I usually put the flour first then salt. but this time I put the salt first.

What happened? it fizzled like a soda, like mixing baking soda and vinegar, so many bubbles appeared immediately. I noticed because of the sound it made (was looking at the scale numbers).

Obviously it cannot be a chemical reaction because salt does not really react with anything there, at most it kills some yeast cells before mixing because some parts would have high salt content. there has to be some cool biology involved. And I refuse to ask any AI for that