The source of this is: https://twitter.com/VitalikButerin/status/1285593115672358912
And in particular, he links to: https://www.cs.princeton.edu/~arvindn/publications/mining_CCS.pdf
I am: an Ethereum entrepreneur working full time on https://flowerpatch.app, an indie game
When I first read that tweet, I was really surprised. We've been thinking since the start of Bitcoin that fees would gradually become the long-term thing that sustains miners. We were told that paying miners = security for the network