I’ve never been able to fully grasp the need to discover magnetic monopoles. I know that it would add a perfect symmetry when compared with electricity but I still don’t get the big push.
There are a number of theories beyond the standard model that predict magnetic monopoles, all of which give various ranges for mass and other quantities. Therefore any observation and its properties may tell us something about what lies beyond the standard model of particle physics.
(Unfortunately, I believe, the mass of the magentic monopole is so huge - 10^16 times the mass of a proton is a figure I seen been used - that it is impossible for us to produce in a collider and is they are so rare it is highly unlikely to be detected in passing by us - although that has not stopped attempts!)
Also, there are a number of theories on what happened before inflation that are used to try to explain why the universe started with low entropy. say for example, Holographic Cosmology (this is to do with the universe being a sea of black holes before inflation, a theory developed by Thomas Banks and Willy Fischer, not the
Holographic Principle developed by Susskind and Hooft which is a different beast), Brane theory or Dark Shatter theory.
Many believe that magnetic monopoles, should have been created during the very start of the big bang, given what flavour of speculative theory you are using. And therefore would have been absorbed by the first black holes that may still exist today - relic primordial black holes - and monopoles being massive particles would be tend to be resisted to be ejected as Hawking radiation. (Yes, primordial black holes are a thing that has not been observed yet also...).
The above three theories mentioned have various proportions of black holes, monopoles and other things, so an actual observation of a relic black hole with monopoles in it
may provide evidence for one approach over another.
TL;DR Observation of magnetic monopoles may give evidence of what lies beyond the standard models of cosmology and particle physics.