Why did modernist fine artists have a sense of rebellion against tradition?

The so-called modernism is actually an extreme expansion of individualism.

All modernist artists emphasized the individual, and demanded that their art be as new as possible, from techniques, styles, elements, and even tools and materials, all of which were unique and not used by others. Expression is also their own deep emotional feelings that no one else has ever felt, everyone wants to do it without predecessors or successors. This is called "creative consciousness".

Ahem. It's like being a rebellious teenager.