Or he wanted the owner to think that he wasn't interested so he could disconnect himself from his investigation as the Green Hornet, but that doesn't make a lot of sense either.
Especially since he was openly investigating as Britt Reid when he saved the bus and found the cut brake rods. He had no reason to keep that secret, since presumably the whole idea was to gather material to print in the newspaper.
I have to say, though, it's pretty badass to save a bus from tipping over by crashing it into a building
I'm a little unclear on why he thought that was the better option, let alone why it actually was.
(The concept of "brake rods" is interesting too. I don't know much about cars and such, but I gather brakes are hydraulically controlled these days, and when TV/movie bad guys sabotage brakes, they cut the hydraulic lines and the fluid leaks out. Were rods part of an earlier, more mechanical control system?)