I have had experiences of joining two different sites which both use Microgaming, neither site connected by license or operator, and had almost identical win/losses across them. i.e. Lost £400 on one, and then won £400 or close to on the other. Could all be a conspiracy, but in my 10 years of online gaming, occasionally I have joined a new site, deposited £50 or £100 and got it up to £600-£700, but the casino very quickly takes it back. Whereas deposit a lot of money at one site, and you can have a period whereby you can get the balance up very high and it keeps you up there, rather than taking it all back.
I cannot understand how I could have deposited £100 on one site, and walk away with 10k an hour later. I don't believe in luck when computers and RNGs are involved. I don't think the operators do either. The only caveat is that I can't recall loosing 10k on netent as I have only started playing them recently, MG or Nextgen definitely though!