OpenStreetMap data isn't public domain, it's copyright under a creative commons licence. There are clear rules you must obey to not be in breech of the licence.
Note that I put scare quotes inside of scare quotes, because I really disagree with that name. Irony quotes might be a better name, which would allow it to cover all different and separate forms of irony (sarcasm, tragedy, fate, etc).
But that's neither here nor there. The point is, "steal" is in scare quotes meaning it is using a word to express something other than its literal intention.
I don't think I'd use the word steal in respect of copyright works. But here it is the moral rights which are being denied.
How do you steal something given to you as a gift? Claim it was yours all along and so deny the owner their attribution. Even if the owner of the copyright retains access to the data you can still deny them their lawful attribution - that is what has arguably been stolen here I think.
OpenStreetMap data isn't public domain, it's copyright under a creative commons licence. There are clear rules you must obey to not be in breech of the licence.