Complex sentence: After that, Korea planted Yoshino cherry and festivals began attracting the wider range of tourists because Korean believes that Yoshino cherry is the same species as Korean indigenous species called "King cherry" whose mass production is still being studied.
Split into simpler sentences: After that, Korea planted Yoshino cherry and festivals began attracting the wider range of tourists. Because Korean believes that Yoshino cherry is the same species as Korean indigenous species called "King cherry" whose mass production is still being studied.