Two 240 volt runs off same breaker
Disconnect the old run then hook up the new one
Since we're dealing with EVSE (a Tesla charger) here, we need to provide a dedicated branch circuit for that EVSE as per NEC 625.40:

625.40 Electric Vehicle Branch Circuit. Each outlet installed
for the purpose of charging electric vehicles shall be supplied
by an individual branch circuit. Each circuit shall have no other
outlets.

As a result, you'll need to disconnect the old wires from the breaker you plan to use and cap them off inside the breaker box, then attach your new homerun to the breaker in question.