That comes down to what I was saying the other day about having "no barrier to entry"
This was the obvious end result of nostr.  There is no such thing as "censorship free" without spam.  If there is no cost to spamming then spammers will spam.  

The reason only reason Matrix, XMPP, Mastodon, Pleroma, Misskey (you can lump in Pixelfed, Steemit, GNUsocial, and Friendica) have been more successful at mitigating spam is because they all have a form of censorship.  Some of them are even more aggressive than the current heavyweights.  

Nostr doesn't put a cost on spam.  It is just wide open.  You have generate nsecs until your heart's content and just spam the network and no one can stop you.  A kiddie script has ruined this utopia.