I do not talk about bitcoin here. Bitcoin is signing transaction perfect. It does not use ring signatures.

Edit:
Alice, Bob and Carol do not want spend their Monero. But hacker Dave wants their money. A ring signature obscures identities because it only proves that a Dave belongs to a group. So Dave ring-signing Alice, Bob Carol and Dave inputs and send XMR to his new stealth addresses.

Edit2:
Monero is same as money on the pavement. So easy to just pick up them from the pavement. Easy money ... but worthless, who can use them?
(Am I wrong ? Why ?)