Rob245

Question: Why does Casey crush Shredder in the garbage truck?

Rob245

Answer: Most likely to kill Shredder and make sure that there would be no way to come back but, as seen in the sequel, Shredder does return.

Question: What was Shredder's plan? Surely he'd have the Foot go beyond petty thievery eventually. I never saw it addressed in the movie.

Rob245

Answer: It's not really petty thievery. Shredder essentially has control over a large crime syndicate which is involved in pickpocketing, burglary, and highjacking. And that's just the gang itself. The Foot Clan itself is probably involved with other activities that we haven't seen.