How do films this bad get made?

I saw this in a DVD bargain bin today and thought, "hmmm, a film with Jeff Bridges and Ryan Reynolds that i've never heard of about ghost cops....I smell comedy badness potential" and just had to see it (i am a masochist I think)

This totally deserves RedLetterMedia's Best Of The Worst treatment!
I'd say it's worth seeing just for the spectacle of a film getting everything as wrong as possible.

I am quite fascinated by this subject, so many questions!
Who thought a Ghostbusters / MiB rip off was a good idea?
How do movies with this bad a script and premise, on this size budget, ever get past the initial proposition / planning stages?
Why do reasonably high-profile actors agree to be in them, other than "for the money"? (i'm not including Kevin Bacon in this question, he'll be in any old *beep* these days, and maybe Ryan Reynolds wasn't too picky back then either)
Wtf did they actually spend the $130mil on?

Additionally, there was so much (bad) CGI, it would be better described as a feature length video game cut-scene than a movie!

It didn't work as a story (utterly derivative - more evil portals in the sky?), it didn't work as a comedy, or a self-concious parody if that's what they were going for (it wasn't funny), it didn't work as an action movie (GCI demo yawn), it's chock-full of wtf? scenes that made no sense. I could go on

Apart from a couple of brief scenes where Jeff's talent just about shone through the murk, it's hilariously bad. I'm seriously starting to think that films like this are nothing more than fraud, a racket. Ever seen "The Producers" by Mel Brooks? And RLM did a dissection of Adam Sandler films - why they get made and how the people involved (often personal friends of Sandler) still make a load of money from the questionably large budgets whether it does well or not...it's very enlightening. https://www.youtube.com/watch?v=sXNsT7-Lwsk