At first glance 'foundations' seems to speak of beginnings while resurrection of the dead and 'eternal judgment' seem to speak of the end. So why are they presented as foundations of the faith in Hebrews 6?

One answer is that knowing our destiny as believers, and indeed the destiny of the world, is a foundational matter. Knowing our destiny grounds us in our new spiritual reality and orientates our lives towards the goal of Christ's return. Knowing the destiny of the world helps us see how we should relate to it and what our mission in it is.

But in an important way resurrection and judgment are also very much part of the beginning, and the ongoing outworking, of the Christian life. This is illustrated in one of the visions of the book of Revelation.