Why does a Bella cargo bike not act like a car driving in reverse? This is crazy you could never make any vehicle have this kinda steering layout. You would imagine that it would be horribly unstable at high speeds +30 km/h. I can't see this being a good idea but it seems to work. 

There's a reason why 100% of street vehicles have front steering. 
So how tricky is it to drive such a trike?
Could I take a normal trike and flip some stuff 180 degrees and have the same results?
You are not wrong to ask how tricky these things are to steer. They are very disconcerting to manoeuvre until you are quite familiar with them.

They certainly would be unstable at 30+ km/h. But good luck with that; you'd need to be quite an athlete to achieve such speeds. If you could pedal fast enough though, I think you would have a quite hilariously dangerous vehicle in your hands.

In practice, they are ridden at much lower speeds, where the rider doesn't find themselves caught out in ever-greater cycles of steering over-correction, and where the outward movement of the back end isn't rapid enough to be destabilising.