The cause of muscle soreness isn't completely understood but some of the leading hypotheses are that it is due to lactic acid buildup or that it is due to micro-tears in muscle tissue (of course it can also be a combination of both of these).

If it's due to lactic acid, aerobic exercise may promote the break down and clearing of lactic acid as u/ImOnAnAllCarbDiet mentioned. If it's due to micro-tears, aerobic exercise may promote faster healing by temporarily increasing circulation, enhancing nutrient and oxygen delivery to the affected area. I think it's highly likely that aerobic exercise reduces soreness from strength training, even if our evidence is anecdotal.