Why are there so many interracial marriage in the world today than before?

These numbers aren’t simply a matter of love. They’re the consequence of economic, political and cultural factors. To list just a few:

Attitudes (plain racism): While 72% of black respondents said it would be fine with them if a family member chose to marry someone of another racial or ethnic group, 61% of whites and 63% of Hispanics said the same. More specifically though, Americans aren’t comfortable with specific kinds of intermarriage. A Pew survey found that acceptance of out-marriage to whites (81%) was higher than is acceptance of out-marriage to Asians (75%), Hispanics (73%) or blacks (66%).
Migration patterns: The Census Bureau provided the following examples: “the removal of many American Indian tribes from their original lands to reservation lands; historically higher proportions of Hispanics living in the Southwest; historically higher proportions of Asians living in the West” all of which shape where intermarriages happen and between whom.
Availability of partners: Systematic incarceration of young black men, together with higher death rates contribute to the fact that black women are much less likely to get married than women of any other race or ethnicity in the US. This, together with higher black unemployment rates mean that black individuals make up a relatively small share of all marriages, including intermarriages.
Education: People with a higher educational attainment are more likely to intermarry. This affects geographic patterns too – areas with higher educational attainment are more likely to have more interracial couples living there.