This is not "workplace bullying." This is office politics. You are a threat to their job security. The silence is their way of telling you off. They are doing it for themselves and for your direct manager.
Your nicety tells them that you are weak, because you want them to be nice to you. They realize that their rudeness will be effective on you. They have contempt for you. That contempt compensates for their fear of you and your new stuff.
"我多次找大manager談，要求工作", the problem is that he was expecting you to tell him what needs to be done and do it.
Your issue is with the direct manager. Keep the pressure on him (you were hired for this.) Show off your understanding of the old system, as well as the benefit of the new. Can you set up the new system first without the data?
You may not be totally confident about whether you can carry it to a successful outcome. Only you know if it is worth doing.
But the alternative is you land anther job sooner.
