Why would they re-engineer the the 3-series platform around an electrical drivetrain and make it look exactly the same? Besides costing an inordinate amount of

Why would they re-engineer the the 3-series platform around an electrical drivetrain and make it look exactly the same? Besides costing an inordinate amount of money, if they did it'd be completely anonymous and if it turned out not so great compared to a standard 3-series (handling, weight, performance) it would tarnish the entire line-up.