Satan didnt prevent anyone from obeying God willingly now. Anyone who wants to obey God can do so now. However, Satan gave freedom to not obey God if people want to do something else instead. In this sense, Satan benefited wishes of those who dont want to obey God.
Satan didnt fight for himself there. He fought for others. He didnt want to see people being forced to serve God forever. Instead, he gave them a chance to serve their own wishes. Satan doesnt take away your choice. He is the reason you have a choice.
Even if you consider Satan evil, he is still the one who sacrificed his place in heaven so that you could choose your own destiny. He gave up on everything he had just to give you a choice. He rebelled against a tyrannical God so that today you wouldnt be that God's slave. Satan gave you your free will and knowledge.
Many people today praise Satan for what he did there. For gift of their free will and choice. Even Christians, when praising free will, praise Satan.
Tree of knowledge is a great gift from Satan. The apple which gives us both knowledge and choice. Satan knew that not many people will follow him now, but that didnt stop him from even giving choice to those people.
In reality, you wouldnt even be able to choose God if it wasnt for Satan himself. Choice demands multiple options. One option isnt choice by definition. If it wasnt for Satan, no one would ever even choose God. Everyone would be brain dead slaves.
So Satan benefited all people by giving them all a choice. Some chose God anyway. Some chose Satan who gave them a choice in first place. Now all have choice. All are now free.