Why and how did Pluto die?
It isn't that Pluto died per se. Instead, Pluto is what it always has been—or at least, what it has been for millions, perhaps billions, of years. It's a small, rocky, planetoid. What happened was, after years of debate, in 2006 the International Astronomical Union finally agreed to reclassify Pluto as a non-planet according to new guidelines over what was and wasn't to be considered a planet. That's what led Mike Brown at Cal Tech to say "Pluto is dead."
The planet Pluto did not die it is still in our solar system. It is not actually a planet, it is a binary planet.
The dog pluto - Are you taking about the dog Pluto.
Sorry! I don't see Micky Mouse.
I don't know anything about thaat dog Pluto!
According to IAU Resolution 5, a planet is:
1. a body that orbits the sun
2. has sufficient mass for it's self-gravity to overcome rigid body forces so that it assumes a nearly round shape
3. has cleared the area around it's orbit
Because of that last one, Pluto is not classified as a planet. If we were to classify Pluto as a planet, we would also have to classify several dozen, maybe even several hundred, objects just like Pluto as planets.