How come Galileo Galilei didn't get blind from looking at the Sun through his telescope

At least he discovered the sunspots :p

He used a helioscope. He was not that stupid. The lens was focused onto a large sheet of parchment so he could observe the Sun. He did go blind, but that was due to old age. Though what we call blindness might have been extremely poor eyesight and recorded as blindness.

At first, he observed only at sunset, when the sun is dimmed by the dust in the lower atmosphere. Later, he started projecting the image of the sun through the telescope and onto a piece of paper. He never looked at the sun with his eye when it was bright and high in the sky.

He was just a bit smarter than that.

Using a special telescope called a helioscope, which is basically a telescope with a really darkened glass lens at the end

technaly he didnt look directly at the sun , he observed other things to see the sun

He did get blind.

Because looking at the sun through a telescope doesn't make one blind. It just hinders one's vision temporarily.