Markets are unpredictable. Markets are made by people, lots of people, who make individual decisions. Sometimes they act like a mob, and all move in a common direction. Sometimes they act totally randomly.
Short term, markets are often wrong. Prices are a reflection of popularity, not knowledge. Mechanisms like buying short a stock that is running too hot, or conversely buying long stocks that are un-fairly flogged. But in general, short term prices are only a reflection of crowd-sentiment, and not much else.
Long term, the trend of a stock will converge and approach the true value of a company. Long term is decades.
Most important, the information available to make good investing decisions is fundamentally lacking. Most critical information is locked away, proprietary, within the company who only releases information required by regulation. So none of us are making truly informed decisions, and any arguments we may have on a company are like flies buzzing over horsesh!t. The horse itself, the meat of the argument, is galloping off over there, and here are us flies buzzing over a pile of crap that the company disclosed because it has to do so regularly.