I took a Biblical Literature course last semester, I loved it so much I kept (and will never throw out) my binder. I didn't resell my textbooks either.
Just checked, Johns Gospel was actually the last one written.
Mark actually knew an apostle but wasn't one himself. That's the closest direct connection to Christ of the Gospels.
The problem with alot of those classes is it is based on theory - not quantifiable fact. Especially the people who adhere to the "Q" theory.
So...there are many theories out there put forth by many experts. And still, it is highly likely that any canonical gospels were included in scripture because they were recognized as having direct relationship to the apostles.
The apostles had their own disciples who preserved the teachings, and the gospels emerged from this setting.
So I don't think it is entirely accurate to say the writers didn't know Christ, as it is possible they were acting as "compilers" and not as authors.