I believe the CDC has said deaths due to Covid is about 6%. The other 94% include Covid with co-morbidities. Some of the co-morbidities the CDC includes are terminal cancer, heart failure, strokes, and more. Covid didn't necessarily have an impact on the outcome of some of the deaths, so the death was a death with Covid rather than due to Covid.
Assuming the 300,000 Dec total is correct, 6% is 18,000. Covid probably won't hasten a terminal cancer death, but may hasten a heart failure death.
300,000 deaths is still 300,000, but the original death estimates were possibly over 2 million. Hopefully, things are going to continue to improve.