Blockchain explorers contain alot of signatures in spent coins transaction in the scriptSig part of the transaction, can the attacker reuse this signature in a new transaction to steal coins received on this address ?
No, the signature is only valid for the given inputs and the given outputs of a transaction. Once the transaction is confirmed the inputs are no longer valid so they can not be used again. The siganture however is not valid for different inputs. So an attacker could only create a replay attack (send the exact same transaction again) which would get them banned by their peers over time as they keep broadcasting invalid transactions.