Lines of evidence from many fields of study, from fossils to dna sequences, have been important in developing evolutionary theory. why is it important to have supporting evidence from a variety of fields?

One reason why it's important to collect evidence from many fields is that the methodology of each field can introduce a bias through its measurement methods.

For example, imagine that we find out that our method of sequencing DNA is proven to be wrong - if we collect information from many different fields, then this will not invalidate the evolutionary theory, as evidence from other fields still supports it.