Don’t Step on the Cracks!
There’s an infinite number of possibilities as to floor tiles can end up cracked. For starters, maybe you hired a not-so-professional tile layer (maybe yourself?) to do the complicated, or perhaps they didn’t use a trowel to leave grooves in the tile adhesive. Or maybe, just maybe, you live where two plate tectonics meet.
That would appear to be the case in this person’s home. Either that or one side of their home is sinking into the ground, causing the floor to snap literally in half. If your floors have a fracture as long and as deep as this, it’s time to check the foundation.