Of course it changes the “odds” in addition to changing the actual format to which the President and Biden had agreed. I’m surprised you even asked such a question. Campaigns agree to every detail...location and setting, date, moderator, even a box to stand on when the two candidates have a perceptible height difference. I don’t know if they execute a signed agreement (contract) but they certainly have a verbal agreement. Going from an in-person format to a virtual one is a huge material change to their mutual agreement. Both sides should have been consulted in advance and their agreement should have been obtained before the “Commission” publicly announced the change. Trump, being a businessman well used to contractual processes, wisely rejected this gambit. If you don’t understand this, that’s on you, not on the President.
So far I see no cogent reason for him to relinquish the opportunity to try to improve himself in a situation in which he is losing at the polls as far as we know. He further risks looking petulant. This comes in the wake of refusing to bargain anymore with Nancy Pelosi over Corona virus subsidies. He runs the risk of looking too much like Caesar in a media environment that longs for the Ides of March.