If there was vote fraud, why not impeach both of them?
If you impeached them both, the Speaker of the House would become President.
Or, impeach Biden, Harris becomes President, and appoints a new V.P.
Impeach Harris, and that new V.P., whoever she is (*cough*Hillary*cough*) would become President.
No matter what, there is no way to reinstate Trump as President (unless in the above scenario, Harris appoints Trump as her V.P.)