The truth of the matter is that the 737classic update from 1984 was already too low on the ground for the CFM56 engines to fit. So they had to reshape the nacel

The truth of the matter is that the 737classic update from 1984 was already too low on the ground for the CFM56 engines to fit. So they had to reshape the nacelles into that odd shark mouth looking oval shape unique to 737s for that little extra bit of ground clearance. The problem isn’t new, was well known and yet greed made them update that same old airframe for 35 more years until it all came crashing down (literally, sadly)