Harry, I empathise. Although I write on Medium more because of a 'need', (if that's not too strong a word), to write, rather than for money, the fact that I am a below-the-poverty line pensioner means that those few extra dollars mean a lot.
However, I have long since ceased attempting to decode the mystery of how Medium determines its recompense to anyone, let alone those such as yourself who write with regularity, high frequency and to large numbers of followers.
Now, I'm just grateful for any amount that arrives but try to make any sense of how and why - it's beyond me ...