I think that you got quite unlucky. It happens every day, thousands of times, to thousands of people. It’s certainly happened to me, and it’s happened just as often in a real casino as it has online. Once, in a live casino, I was down about £2k. I decided to go for double or bust, and played two hands of £1k each. I got 21 on both of them. The dealer was showing a 7, he then flipped over another 7, and finally drew a third 7 to match my two 21s. The next deal I lost on both hands. You want a mathematical explanation for that too? It’s called variance.
If it had been you who drew a 6 card 21 you wouldn’t be complaining. But that’s just as likely, and I’m sure it’s happened once or twice to you. It certainly has to me.
If you think it’s rigged, why are you in the business? I don’t think it’s right for you to promote online gambling if you:
a) don’t understand how it works
b) think it might be rigged