kind of a surprising coincidence.
for both Ethereum and Bitcoin the circulating supply graph looks like a smoothed version of the (log) price graph, which is not a relationship i'd expect.
i think the explanation is just that, for both, supply grow declines over time, and both have "matured" in the sense their price growth rate is much lower than in their days of early foment.
still interesting.
from
https://studio.glassnode.com/metrics?a=ETH&category=Supply&m=supply.Current
https://studio.glassnode.com/metrics?a=BTC&category=Supply&m=supply.Current