Help understanding Ida

I’m a Darwinist, so this is not a question about creationism or intelligent design or the virtues of Darwinism or anything else.  I’m simply confused about why everyone is so certain that Ida’s the missing link.

This lovely site simply says “She lived around the time that primates split into two major groups.”  Given that it’s unclear to me that we a large enough fossil record and the precision to know whether Ida lived before or after that overwhelmingly important split  (since “47 million” is a fairly rough number), and given that we don’t know if her progeny survived or whether there were any others like her, why are we so certain she matters?

The helpful timeline at the same site actually doesn’t help me. I’m still not clear why the certainty that Ida is the handle on the fork that ultimately led to two different types of mammals, one simian and one us.

Having said that, I nevertheless think it beyond cool that we have an almost perfectly complete skeleton from 47 million years ago.  In some ways, looking back through time, 47 million years is as difficult to contemplate as 9 trillion dollars.  Both are numbers that make almost no sense in context.