The article states:

Gnome-making was big in Germany through the early 1900s. But World War I (1914–1918) nearly stopped production. That might have been the end of the trend, but things changed in 1937.… A much-loved movie came out.

Which phrase from the passage helps you understand the meaning of the word trend?

a much-loved movie
gnome-making was big
things changed
stopped production