Gambling is unpredictable. Thus, there is no single betting strategy that will lead to regular wins.
You can't generalize like that as there absolutely are people who make a living through sports betting. Maybe not OP (since they haven't shown proof), but legitimate professionals exist. These bettors consistently make quality picks and have proven long-term profitability. Just because most people lose doesn’t mean skilled, disciplined bettors can't win over time.
In my personal belief when comes to professional sport bettors is that they do not have an unique betting strategy which is always going to work. They rather have several strategies which adapt to varios situations they see in the markets, in order to increase their chances of winning.
It is not a fixed thing or pattern they follow to win money from predictions, but rather an adaptative process which is changed any time it is needed for them to get money or increase their chances.
Also, professional bettors do not take all bet they see on the market, they tend to be selective on those which are more likely for them to profit from.