An oil tanker has as much chance of ramming a destroyer that is aware of it as a destroyer would if it were trying to ram a Swift Boat. Nada. Zip. Zero. Nichts.
When I was on a destroyer during the Vietnam War we had lookouts on all quarters 24/7 no matter if we were on coastal patrol or out in the big blue Pacific. There is no excuse for not seeing a fricking oil tanker. Even if they did get hacked.
Some kind of sabotage to the steering mechanism would make seeing it irrelevant. But it would take a level of skill that only a few sailors could have, those being specialists in engineering. And the timing would have to be perfect.