The answer is: Don't use .accumulate()
as that's exactly what it does.
Explicitly create and add a JSONArray
to your json
object prior to your loop. Inside your loop, retrieve it and add to it:
JSONObject json = new JSONObject();
json.put("list", new JSONArray());
...
while (oResultSet.next()) {
JSONObject obj = new JSONObject();
obj.accumulate("nombre", oResultSet.getString("nombre"));
obj.accumulate("goles", oResultSet.getInt("goles"));
json.getJSONArray("list").add(obj);
}