Since when was it proven that the leaks were due to iCloud vulnerabilities? There were a lot of allegations, sure, but no hard evidence. If someone guesses your GMail password and leaks your mail - was it a GMail leak?
But, I totally agree that this U2 move was absurdly ill considered.
Google recently stated that the 5 million sets of Google account credentials were not stolen directly from them and only 20% of them were valid. Is this also 'unproven'?