I’m sure it was known but I bet everyone just assumed they were staring at death. Once that first surfer and jet ski driver got brave enough to demonstrate it was survivable it was game on.
I can ensure you that's not the case. I was born a couple dozen kilometres from there and as a kid, there was little to no people surfing in the region.
The surfing culture in Nazaré was inexistant before 2011, it was just a beach place known for good fish and nice people.
Seems like you're saying exactly what parent comment is saying.