The casinos are not manipulating anything, you are just lucky. I used to think that every beginner had some sort of luck but that's not actually the case, if an Intermediate player had bet on that same game the gambler would have also won, the casinos don't really look out for beginners to lure into gambling, that's just what we have been made me believe according to our previous experiences. Luck is just a matter of hitting the right timing
So you don't believe in beginner's luck? 
Just kidding, I don't believe in that as well because I believe luck doesn't see if you are a beginner at a place or a seasoned pro, luck doesn't depend on your status or anything like that, it just happens whenever it needs to. It's nothing more than a general coincidence when a beginner manages to win something good in gambling, and then, when they later lose, they feel like they were winning when they were a beginner, but aren't winning anymore because now the casino has detected that they've become a seasoned gambler.Your results aren't affected by the amount of time you've spent in a casino. You might often see people getting huge wins in their very first bets in a casino, and some might not win anything even after playing for so many sessions, so, this proves that it's all dependent on one's luck and other things are not important and what we think of is nothing but our mind playing with us.