When I voted, I had both Biden and Harris’s name on the ballot. I voted knowing that, if Biden couldn’t serve, Harris would. Every single person who voted for him knew the same thing.
So yes, the person we voted for to be president in lieu of Biden is now running for president in lieu of Biden.
Really, it’s not that complicated.
Maybe you’d understand it better if you, oh, I don’t know… Had voted in the Democrat’s primary. But since you didn’t, haven’t, and wouldn’t, I’m not sure why you think your lack of understanding of the process you don’t participate in somehow means the process was manipulated and those of us who do know the process and participated in it should be as wound up about it as you are.