That graph is silly. Who is the "we"? It appears to give credit to ancient Egyptian learning but not that of the Islamic world. As the dark ages in Europe roughly coincided (on that graph's timeline anyway) with the high points of Islamic achievement (not previously replicated by ancient greek or roman scholars) it is not obvious that any time was lost by the world at large.
I'd also suggest that the rate of progress is accelerating, but that there's no reason to assume it would have taken off like a rocket exactly when that graph suggests it would have done. Without thinking about it too hard, I reckon I'd expect to see something more hockey-stick like than that. It's a bit of a reach to suggest that the only reason man hadn't invented the computer in about 1385 was the influence of Christianity. 🙂
Going back to the Islamic learning issue, there's no doubt that that scholarship flourished in a very religious society. It just wasn't religious in the very specific way that got you killed for pointing out that the earth was a bit more spherical than previously thought (much has changed in Islam and many islamic countries since). So it's another big reach to say that Christianity per se had an impact – christianity clearly could have been immensely beneficial, if it had been slightly different.
Anyway, I'm donning my Woppit-proof suit and retreating from these tentative observations. 😉