Even though the final outcome was far from desirable, the "Absolutely Safe Express" still fulfilled its purpose, bringing Motan and his team of four back to Sky Pillar Mountain.
Although it took several times longer than Motan's trip to Dragon Soul Town, it still made it back...uh, without any...well, it just flew back. Notably, no 'man-made disasters' occurred during the journey. Jadka's magic wand behaved, Ya Ya remained steady, and Ji Xiaoge didn't serve any late-night snacks. By all means, it was perfect.
As for why the express fell from the sky in the end, there wasn't any special reason...
A thrilling takeoff, a turbulent journey, and a logical crash landing, that was the extent of it.
Ruvie's judgment was not wrong. Even if slightly damaged and overbooked, in theory, the express could have safely transported Motan and his three companions from Dragon Soul Town. Of course, whether it eventually fell or crashed was something Ruvie was quite indifferent about.