In Japan, they had the Famicom. You put in the cartridges on the top, just like with the later SNES and other consoles.
But for Europe and the USA (and the entire "West"), the "NES", as it was called here, they not only changed the visual colours and design radically, but also made the cartridges (much physically bigger than the Japanese ones) slide into the console from the side, and then you had to push them down for them to "activate".
Obviously, this design caused more moving, mechanical parts that could (and did) break, seemingly for no good reason. I can understand why they wanted to "hide" the cartridge, but why was there a need for it to also be "pushed down" while already inside of the console? Why not just have it stick in from the side, just like they did, but not require the whole part where you "push it down"?
I could never understand the need for this, and I still don't understand it to this day. It seems pointless. It feels like the cartridge is already "plugged in" electrically when it's in the non-pushed-down state, so what about pushing it down makes a difference?
It should be noted that they later actually released a "top loader", but I only ever learned about this many years later, from AVGN. So it was not exactly common here. Also, there are modern devices which do exactly what I point out: they just have the cartridge "slide in from the side", but there is no need to "push it down". My question is about why they would choose this technically absurd design back in the day.
I know about their desire to make it look more like a VCR and less like a toy for the USA, after the Atari video game crash, but my suggestion is not that they would make a top loader right away, but I'm simply asking why they made the original design pointlessly require the player to push down the cartridge while already inside the machine, apparently resulting in nothing less than more parts that could break.