AITA for starting a new game over my brother's old save after he gave me his console?

My brother sat down, opened the game and said, "Where's the mountain fortress?"

I'd started a new campaign in the slot where his old one had been.

He gave me the console and its games three weeks ago because he hadn't used them for years. He said, "It's yours. I'm done with it." When I opened this game, I saw a long-running campaign under his name. The menu warned that starting again in that slot would replace it. I did it anyway because I wanted to learn the game from the beginning.

I didn't ask him. I assumed that giving me the console included letting me use its games normally. I hadn't thought about whether he might still want the saved campaign even if he didn't want the machine in his own flat.

He says that fortress was something he and a school friend spent months building, and that he would have told me not to overwrite it if I'd mentioned the warning. I said he should have told me when handing it over. He said the warning itself was the moment to ask.

He hasn't demanded the console back. He just told me he wished he hadn't given it away. It's now sitting on my shelf, and I haven't started the game again. AITA?