Yeah, it’s different because Trump is not the incumbent. He was, and had that advantage before, but he lost it. It’s not clear whether being a previous loser candidate is more of a partial incumbency advantage or actually a disadvantage because he already got kicked out.
Anyway, the internal infighting about replacing Biden will be done soon enough. Convention is in a month, and there’s talk about doing a roll call vote to nominate him pre-convention as early as next week. Or, if you’re right and Biden’s replacement is inevitable they’ve got about two weeks to get that in order.