Why do Satan and his demons hate us and want us to not make it to Heaven?
The Bible does not give us a specific answer on this, but in the general sense I think Satan and his forces are against everything God is for, and that includes us.
More specifically, I’ve heard some scholars speculate that if Satan can use his trickery to keep us from seeking the Lord, maybe he will be able to force the Lord to pardon him to avoid having to condemn all the people Satan has deceived into siding with him.
Others say Satan sees us as we really are and knows we don’t deserve what God has done for us, so he tries to keep as many as possible from accepting it. It’s the old “If I can’t have it, then I’ll see that nobody gets it.”