This type of trading conspiracy theory does strike me as a bit odd for reasons mentioned here - i.e. that if people copied you, then it would move the market further in your favour. In actual fact, the only place I've ever read about people learning how you trade so they can stop it working is in the marketing pamphlets of various snake-oil systems on the market 😆
Like all good conspiracy theories, it's better to blame the nameless, faceless 'them' than take a hard look at yourself and work out what you did wrong when your trades do start to break down. I remember Alexander Elder saying in his book how a guy he knew used to trade like magic and make loads of £$£$, but when he was up a sh*tload of cash, it would all go to his head and he would do something stupid and blow up a large portion of his account. He always came out with this excuse that it was his broker conspiring against him.
It's human I suppose - not facing up to your shortcomings.
Ultimately, if you are a successful trader, you will adapt to the market.