Why did English drop all gutteral sounds that languages like German have, but keep the dental fricative?

English is one of the few major languages that maintains dental fricatives, but other Germanic languages don't have them. English doesn't have gutteral consonants though but other Germanic languages do. Why is English the total exception to this (not counting Icelandic, which is very small and hasn't evolved as much).

I find it especially odd since England was invaded by the Norman French and French doesn't have dental fricatives but does have a gutteral "R" consonant. I'd assume that would have tipped things in a different direction. So why didn't it?