What makes the waves at Nazare so big?

When I was a kid, surfing was just getting started. Endless Summer was released in 1966, the first major movie about surfing the coolest waves in the world. I spent many an hour at Indian River inlet (southern Delaware) growing up and getting to know waves that were at most 3 feet. After college in Las Vegas (1980), I moved to Northern California and the Bay Area. During the surf season, November thru April, the waves were big and powerful. The best waves were in Santa Cruz. My go to's were Steamers and Pleaure Point. Both offered great rights with long rides. My first tube was at Zuma Beach near Malibu. I dropped into a good size wave and it wrapped around my sholders and head while the green room opened up. They say getting tubed is like returning to the womb. However, this is a womb with a view!