This graph is a bit misleading for this point, because if some relay it mentioned in someone's relay list it doesn't mean that relay is important. I.e. current.fyi relay is dead but still around top 5 here just by inertia. Also how did you evaluate relays? By how much events they cover?
Thanks for the additional info. I just started looking for a few relays to send events to, and expected it to be a quick task. It was harder than I expected. I've now widened the net. Thanks for these stats, they're a great starting point. I think we need more. Also nostr watch is a great resource.