There were a lot of issues with it being anyone else. Since she was already the VP and already “on the ticket”, switching to anyone other than her would have brought with it a whole lot of complications and probably would have tied up all the money the Biden campaign had raised. The whole process of deciding on anyone other than her posed huge risks, especially given the time constraints. Harris was effectively the default option so they took the path that appeared to be easiest and guaranteed that the campaign kept its funding.
There were a lot of issues with it being anyone else. Since she was already the VP and already “on the ticket”, switching to anyone other than her would have brought with it a whole lot of complications and probably would have tied up all the money the Biden campaign had raised. The whole process of deciding on anyone other than her posed huge risks, especially given the time constraints. Harris was effectively the default option so they took the path that appeared to be easiest and guaranteed that the campaign kept its funding.