This is something you'd learn in your first year at law school. If, as Trump's complaint alleges, Dominion did destroy evidence then the evidence is immediately assumed to support the opposing party's allegations.
Biden's defense would now have to prove there was no fraud as if Trump's team had certain evidence of there being such.
OP, your analysis is so bad, it actually could have come from a 1L.
There is the “burden of proof” and there is the burden of persuasion.
Only where evidentiary burden shifting doctrines are in play (spoliation, joint and several liability etc) does the burden of proof shift to a defendant.
OP invariably means the “burden of persuasion” which would shift upon a prima facie showing of the elements of the allegations in the Complaint.
Don’t quit your day job