Despite having no scientific basis, astrology is very popular, and it seems many people believe in it.
Literal
Astrology [topic-は] scientific basis [also-も] nonexistent [although-のに], very popular exist, astrology [topic-は] believing people [subject-が] many seems.
~のに (although/despite) introduces the concession: no evidence, yet popular. The sentence repeats 占星学は, resetting the topic for the second clause — slightly redundant but natural in conversational Japanese. ~ようです hedges the claim as an observation.