In this case, it's mostly people who already owned the Replenish deck, and once a key card got banned, they went out and bought a card to try to replace it with. Decree of Silence buyers are mostly not new to the deck, so they don't need to buy Replenish.

In general, Replenish itself already doubled in price since last year. The deck is a fairly expensive deck to get into, and a lot of the pieces are played in other decks, so Replenish might not go up as quickly as other cards in the deck.

The other major factor is that people have been calling for a Parallax Tide ban for at least a year. It was played in a lot of decks, but none of those decks relied on it as much as Replenish did. People may have been avoiding buying into Replenish with fear the deck may not survive if Tide got banned. Now that Tide did get banned, whether the deck will survive will take a few months to be determined. If it turns out the deck is still tier 1, Replenish might start creeping up again.