“Although astronomers deduced the existence of dark matter apart from the Big Bang model, this substance has become very important to secular cosmologists. They recognize the enormous problems in their theories of star and galaxy formation. Many claim dark matter is the “missing ingredient” that can somehow enable their theories to work.19 This is very convenient for theorists. Since no one knows what dark matter is—or even if it really exists—no one can demonstrate that their theories are wrong!20”
See more here: https://www.icr.org/article/continuing-troubles-for-the-big-bang-model/