Some conifers naturally have bits that go brown and fall off. On others, it suggests death, at least of parts of it. The tree no longer has all its roots, so it no longer has the strength to maintain all its foliage, it will probably shed some.

Some species of trees really resent root disturbance and are likely to die if you try to move them - cedar, eucalyptus are well known cases. With more forgiving species, it is usually to do it in winter when the tree is dormant, or in early autumn when the tree is generating root growth rather than above-ground growth. If you didn't bring enough roots with you, or did it when it was highly active above ground, these could be reasons for lack of success. Having moved it, you need to water regularly until the roots regrow, typically a full season.

If you want to understand more about it, I suggest to start with finding out what kind of tree you have.