Is it necessarily an advantage of a mathematical work to find connection between two different fields?
It is clear that knowledge in other fields can be helpful, especially if one has an unusual combination of expertise such that one can see things others would miss even on well-studied problems. In fact, the variety of thoughts between colleagues of different background makes collaboration in math-related fields so much exciting.

It is hard to find examples where interdisciplinarity played a negative role in one's career, just for the same reason we don't learn about most of the useless approaches in mathematics (definitions that turned out to be useless, in particular not well-defined, propositions that turned out not to help for the problem they were thought for, etc.). 

But from common sense I think that interdisciplinarity can never be negative unless you "cross paradigms", for example by mixing different contradicting systems of axioms to solve the same problem. Fortunately, in mathematics it's (today) quite clear what is not allowed.