Imagine I want to make money from gambling and I am looking for who can help me out, someone somewhere might understand what you need and disguise himself to be a professional in what you are looking for just to make money from you because he is also looking for a means of making money but you will become his means and your problem is not solved. No professional gamble but luck can give you a huge win.
If you are a smart bettor, you would check the reputation of that self-proclaimed expert and verify the validity of his claim. Also, if you know the sports very well, you will know if what he is saying is just crap to earn followers or there is substance on what he is saying to people. Because if you are a long-time bettor of a particular sports, you should at least have the familiarity when it comes to the performance of the athletes.
You have to consider the fact that these so-called experts are also human, where they are relying from their years of experience and knowledge acquired and they are also prone to miscalculations of their expectations. There are underlying factors that they don't have full control such as :
> weather and other environmental conditions that can affect the players' performance
> actual strategies deployed by the coaches
> actual mental/health status of the players involved or their emotional stability
> their motivation in that particular game or the players' adaptation abilities.