One of the fun things about science is it allows people to be prophets without the need to grow a big beard and walk around the desert in a robe. True, Dmitri Mendeleev did have a big beard when he predicted the appearance of scandium—but he didn’t need it, and that’s the point.
Dmitri Mendeleev is known as the father of the periodic table of elements, and rightly so. He ordered the elements correctly based on their properties, which helped predict the discovery of new elements. But he wasn't the first to come up with the idea of periodicity of elements, or the first to try to make a chart.