Options is a zero sum game. For every put contract sold to open in which the seller expected TC to be flat/up, there was a buyer who expected the price to go down.
The seller may have been either bullish or bearish. He may have been short already, selling covered puts against his profitable short position to collect premium. Or he may have sold naked planning to buy, hoping to lower his cost basis on entry.
But it is inescapable that the people who are long the puts are bearish. They may be wrong since most options expire worthless but they are bearish nonetheless.