Why does Altman like coming to earth? Why not go to other planets?

In The Legend of the Super Galaxy (opening about 30 minutes), Meng Biyou explained to Lei:

Altman's ancestors are almost identical to human beings. Because the star of M78 nebula (equivalent to the sun of the earth) exploded. When the M78 nebula was about to die out, scientists built a plasma spark tower. Because the energy is too strong, the people in the M78 nebula have become giants with great power. This is the birth of Altman.

You can watch the video:/v _ show/id _ xmtc0odu1mzm2.

It may be because of appearance and the fact that the earth is relatively weak. So Altman is willing to help the earth.