We were paying higher fees because no one tried to pay less, I think. From what I understand, people started posting transactions with this fee, and they were accepted naturally until everyone accepted them.

I don't know, and I don't have enough knowledge to pinpoint the starting point, but I understand it was natural. Miners could ignore these transactions, but why ignore them if the mempool was somewhat empty?

I understand that user pressure on their nodes led miners to accept these lower fees; it would be very bad to mine empty blocks.