Because it would explain them in light of the other facts we have seen.
Fact. It's fake.
Fact. When he first produced it, Obama trumpeted it about as though it were real.
Fact. Hawaii is more or less backing it.
What ties this all together? How can it be both FAKE and backed up by the state of Hawaii?
Because it was created by a court order and is therefore legal. If Obama was legally adopted by his Grandparents in 1971, then he could subsequently have that adoption annulled, and go back to his original name. This will, however, not result in the release of his ORIGINAL (sealed by adoption) birth certificate. It will, however, allow him to get a court order to the Department of Health in Hawaii for the creation of a replacement one.
Being a legal forgery fits all three facts. It's real and fake at the same time. The salient point is that it isn't the ORIGINAL document.
If that doesn't make sense, i'm not sure I can explain it better.
Besides that, Who else would have access to the bits and pieces of a real 1961 birth certificate to make it look realistic? DOH HAWAII!!