connective N2 uncommon politewritten
ことによる — to be due to ~
ことによる
Builds on こと
A full written guide for ことによる is on the way.
This point is mapped in the grammar tree, but its examples, formation table and usage notes haven't been written yet. The fastest way to learn it now is to meet it in real sentences inside Jengo.
See ことによる in real sentences
Jengo shows ことによる the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled with reference to A Dictionary of Intermediate Japanese Grammar. Editorial confidence: medium.