I was making my "Super Elytra Roller Coaster" when I noticed that the minecarts that were falling were starting to stack.
I s that a glitch or its the world's fault??
Of course it is, that's why you can have some fun with minecarts.
Gamers never die! -Mercy
They are indeed stackable unless you push them.
This has been in the game for a long long time. Look up old videos of minecart "pez" dispensers.