How is it Possible that Steven Spielberg would cooperate with George Lucas to direct a "Dinoriders" the movie in 80's style like "Transformers" with 3D FX like "Avatar"?

I think Dino-Riders could be a nice adventure film for him. Seeing as how people still love Indiana Jones and many of his fantasy films, I think he is perhaps enjoying a little bit of the spontaneity and fun of the early days. If you look back at Jurassic Park you see a guy who was ready to go on to more serious stuff. He basically did it so he could do Schindler and JP (while a big hit) wasn't a great story. I think Indy 4 reminded him how great it is to craft an adventure with a fun story.

Spielberg and Lucas have been friends for many years.The question is;Why not?