To win 21000x needs many lollipops again and again (to trigger another free spin) + a whole screen of 100x bombs and not only once but need it a few times lol.
If im not wrong the max multi ever hit on the sweet bonanza only around 6000x ish.
Maybe a triple x100 and tons of blue candies on the same screen, but i don't think that would make the magic to give us a massive profit. Or as you say, maybe we need lollipops to get more and more free spins.
And something that i have never seen is a lot of multipliers on the same screen, maybe if we get more than 8 it counts as a combo, and pay for it and not only for the multipliers, I'm not sure.
Such extremely high multipliers are very difficult to hit because the probability of them being hit is extremely low and someone with an extreme level of luck can hit that, maybe one person out of billions can be that lucky. They set numbers highers only to attract more gamblers towards the game.