Probably the best reason is that those same Filipino vets were subject to decades of "broken promises and discriminatory treatment" (to use Ige's words) up until Congress and President Obama recognized their contributions to the war effort as noted in the article.

You'd be familiar with their situation had you followed this issue over the years, which many of us have.  Erecting this monument, like awarding them a Congressional medal, is largely symbolic rather than substantive.  But it corrects an injustice that goes clear back to the years of WW2, and as such has great meaning for the families of these veterans.