The games aren't compensated. The RTP is worked out before any real money spins are taken, and calculated from the maths inherent to the game. If I had a bag with 100 balls in, and only 1 was red, the chances of me picking out the red ball is 1 in 100. It doesn't matter how many times people have picked balls out of the bag before me, the odds are always 1 in 100 (as long as the balls are replaced after every go).
As such, every single spin is like plunging your hand into a giant bag of balls. But we are talking about millions of balls here, or even billions of balls. We can know what the chances are of you picking any ball out, and as such we can know from this the RTP.
Everyone is simultaneously picking a random ball from the same bag, every spin. And it's the same bag every time with the same set of balls. It doesn't matter if I win, the chances of me getting that Helios Fury on my very next buy are exactly the same as what they were with the first buy. Its provably fair, both mathematically and statistically; and what has happened in the past or may happen in the future will have no real world bearing upon your result.