Why did Biden oppose Trump's Chinese travel ban in January?

Because he and his family are in bed with China.

Biden didn't oppose Trump's China travel ban in January.  You're repeating one of Trump's lies.

Nevertheless, the travel ban was ineffective.  Tens of thousands of people came from China into the US, after the ban was instituted.  There was inadequate screening.  There is still inadequate testing in the United States.  Also, the virus that devastated New York came through Europe. 

Biden, however, did refer to Trump's xenophobic approach to addressing the coronavirus.  Trump is still engaging in a xenophobic approach in an effort to shift blame from his mishandling of the entire situation. 

Biden wrote an op-ed in January describing Trump as "the worst possible person to lead our country through a global health challenge."  Biden was correct. 

Because the virus was still in Wuhan's lab

Wait, didn't you know the media has already rewritten history on that?  Here is their latest reasoning....

Around the time the Trump administration announced the travel restriction, Biden said that Trump had a “record of hysteria, xenophobia, and fear-mongering.”

....Around the time means immediately after Trump announced the ban.  But Biden wasn't referring to that.  He was just randomly making a comment according to the media.  

Because it was something handy to criticize the President for. Don't expect any apologies from any Liberals that did the exact same thing!

The travel ban was stupid because banned Chinese people and it let Americans travel to China and back, but the Chinese were testing their people for covid but we were not.

Was the ban before or after trump signed the trade deal with China? This was done at the end of January.

Fake news. Biden never opposed it. I dare you to find a link and prove me wrong.