can the casino control the user account that keeps winning?
Yes, by restricting its account, there are casinos that do this; worse is, they create a case against you like a violation of their terms, but it only happens on dubious casinos, so better check your casino if they have users who suffered from such restrictions, because you could be the next one.
does a new account have a greater chance of winning?
It only happens if the casino is manipulated, but if the casino is reputable, everyone on the casino has an equal chance.