In this sentence, "to becoming" is a prepositional phrase. "To", here, is a preposition.
This might seem unusual, because normally after adjectives we have [ "to" + infinitive ], like:
I'm so excited to see you!
It can be painful to lose a friend.
Believe it or not, it's uncommon to hear an accordion on the streets of Paris.
This isn't always the case. Some adjectives, like "pertinent", "related" and "adjacent" take prepositional phrases with "to" that indicate a relationship between the subject and the object, in this case, a gerund.
In fact, "pertinent" is special because it can take both structures:
"It's pertinent [to this discussion] [to mention that we don't yet have public support]."
The "to" phrase in the first set of brackets is a prepositional phrase that says there's a relationship of pertinence between the subject and "this discussion". The "to" phrase in the second set of brackets is the thing which is pertinent.