Q. Why does Mendeleev get the credit for the periodic table?

        Details of answer;
      In the Journal of the Chemical Society (1889), Mendeleev quoted the premise of his 1869 exposure of his periodic table, saying;” Without entering into details, I will give the conclusions I then arrived at, in the very words I used:-- "1. The elements, if arranged according to their atomic weights, exhibit an evident periodicity of properties.” He then recognized the additions and advances that had occurred in the interim.
      When he originally organized the table into rows, a pattern became apparent – but only if he left blanks in the table. Mendeleev was bold enough to suggest that new elements not yet discovered would be found to fill the blank places, going so far as to predict the properties of the missing elements. Although many scientists greeted Mendeleev’s first table with skepticism, its predictive value soon became clear.
      The discovery of gallium in 1875, of scandium in 1879, and of germanium in 1886 supported the idea underlying Mendeleev’s table. Each of the new elements displayed properties that accorded with those Mendeleev had predicted, based on conclusions he shared with de Chancourtois and Newlands; that elements in the same column have similar chemical properties.

        Resources;
aip.org, inauka.ru