First, we had seals at the zoological gardens. Then, we had Gershwin; remember An American In Paris?. And, now this.
Actually, none of it is surprising. Using real world devices in musical ways isn't anything new. And, the biggest part of "busking", as our European friends are fond of calling it, is having a "hook". A sub-par performer with a "hook" can succeed where a "legitimate" performer with nothing more than straight musical skills may be an abject failure.
The difference here is that the guy with the "hook" has something that captures the interest of the public. It all boils down to playing what someone else (part of the "listening public") wants to hear, as opposed to playing something perfectly wonderful but not au courant. Knowing the difference is literally the difference between success and failure in the world of performance.
And, none of this invalidates the "worth" of what anyone does. If you are into playing Mozart, and you do it very well, seeing this guy get large amounts of money thrown into his case (or whatever receptacle he uses to capture his rain of loonies) may not see this as being "right", especially since your skills took years to develop while a reasonable intelligent pinnaped could master what he does. But, just like Elvis in 1959, he's playing what people in his market want to hear.
Plus, who'd want to wear the jumpsuit after he's used it on one of those "steaming", 30° C summer days that they are so cursed with during an average July?