Because the reply guy spams across the bridge into the fediverse a number of instances have muted or defederated the bridge.
It's not even a very sophisticated spam attack and blocking or muting the bridge is a dumb solution.
Anyway I have mitigated this type of attack on wss://n.ok0.org - it was a bit challenging to do because I want to keep the flow of non spammy notes going, my write policy is reasonably fancy now.
To give you some idea of the scale, here's the past 12 hours in the logs:
This is not even the only spam attack, there have been others going on for a while now, this one is just the most visible/annoys the most people because the spam is replies, so it generates notifications.
Mitigating this for my relay doesn't really matter in the great scheme of things, people would have to exclusively only use my relay for this to benefit them, the spam will keep coming through on all other relays and not all of them will deal with it. Clients have the most impact in dealing with this shit.
The shitty bit is this only amplifies calls for walled off relay access (behind fees or whatever), which undermines the idea of Nostr.