Vikings need more space because their space where they were living it was getting too crowed.

Lost in Space - 1965 The Space Vikings 2-20 is rated/received certificates of:

Australia:G

Lost in Space - 1965 The Space Vikings 2-20 was released on:

USA: 8 February 1967

The drive of curiousity, more space, extra rescources, and power

they were either greedy, or they were running low on farmland and natural resources. (vikings were not good farmers, so they had to capture areas that had food.)