If I bet on, say, TSLA, I'm going to convince everyone that it's good bet. Why would he state his opinions about stock markets, without having his investments r

If I bet on, say, TSLA, I'm going to convince everyone that it's good bet. Why would he state his opinions about stock markets, without having his investments reflecting that opinion? I don't see how your statement adds any validity to his prediction. It's logical step. Short sellers put out such opinions all the time.