If the ground was very damp, or you had newish grass down, that would explain why you managed to pull it out by the roots. Otherwise, you were obviously just a bit too enthusiastic! Assuming that a lot of what you removed was actually thatch and moss, then hopefully you haven't managed to decimate your lawn completely. You'll just have to wait and see if your reseeding has been sufficient, but if the ground beneath was not something resembling an inch or two friable tilth, growth of the seed will be limited.

I have just thouroughly soaked my lawn, a good quantity of Wilkinson grass seed plus a good a layer of sivved compost .This will all be washed in in the next few days and will result in a rejuvinated lawn. You have scarified vigourously but this is a good thing. Try to hollowtine when it is really wet

Thank you. I'm pleased to say my lawn has fully recovered.