The same way drivable cars can turn into robots.If it's as lame as the first one I'll pass. Half of a city is destroyed by huge robots, and yet no one talked and the aliens are kept secret? Give me a break. Dozens of people are most likely dead, and no one talked about giant robots?
Unfortunately, a line where this was addressed wound up getting excised from the final movie. I'm not even sure the scene was filmed (but I think it was). At the end, the government explains this as a military experiment gone wrong, so they don't deny the existence of the Transformers at all. And it doesn't matter whether everyone knows about the TFs or not. They can hide.
At the end of the movie Prime goes "We hide here in secret" or something like that. How can they be a secret?
And a lot of that city has damaged by robots running on them.
Who cares, this crap ain't real anyway.
