RTP and variance are two separate things. If something is 50-50, it didn’t necessarily needs to be one after the other. Dice, 50% win chance pays you back, 1.98x. That .02x missing is the house edge. Hence 99% RTP. Thats what house wins in the long run.
Now you could loose 50 coin tosses in a row. Chances are pretty slim, but not impossible. You could win 50 in a row too. The house is essentially saying if you win you’ll get back 1% less than what you bet.