The base 5er has been steadily moving towards being a luxury sedan, like the E-class or A6, more than a large sport-sedan. That seems to only be reserved for the M5, and even then people have stated that though it is lightning quick and sharp, the steering and inputs have become numb.
Isolation cuts two ways, I suppose.
Given that the i5 M40 seems to be about 40% more expensive in base spec compared to the 520i/d, I just know that the 520 will be the big seller.
Journalists love to wax lyrical about the so-called redundancy of ICE cars and how manufacturer's are pushing people towards their EV products, but they speak with the authority of people who don't actually pay for the vehicles they drive.
Until the base i5 is as cheap as the 520i, it'll never be the biggest seller.
Only company car fleets will really buy in, but everyone else will get the cheapest they can afford.