Thanks for the question.
Joe Biden's marital validity is probably a small thing (still serious sin) compared to his more grave abortion advocacy, which is a sin that cries out to Heaven. There are many issues that should have Joe Biden admonished, if not excommunicated by the bishops, (for example he officiated a homosexual wedding), yet we still hear silence.
Sadly, many bishops support Joe Biden, and they have sold their souls over for a political agenda. About 45% of the USCCB revenue for immigration-related social services comes from the US government so the marriage of political interests is much more than a conflict of interest, but a serious compromise of Catholic orthodoxy.
The voices from the episcopate willing to publicly call out Biden on his radical abortion platform (including denial of religious freedom for religious Institutions that don't want to fund it in their health care plans) are few and far between. This is why the Catholic faithful suffer so much confusion. The leadership: 1.) isn't there, or 2.) is going the wrong way.
We must pray for priests and bishops; satan is attacking heavily these days and only penance and prayer can reverse these awful scandals.