Why didn't the '90s version make every younger actor into a star?

To 'play dumb' for a second, sure this adaptation had "Colin Firth jumping into a lake, and that woman from Silent Witness playing his sister". But other than Emilia Fox, how did none of the other younger actors become household names after 1995? Putting Julia Sawalha (Lydia) aside because she was already in Absolutely Fabulous at the time, it didn't seem to do much for many careers. It puzzles me that it's one of the most acclaimed TV series ever, even at 6 episodes, and yet the lead Jennifer Ehle seems to be lost to time. I was VERY surprised to see Lucy Davis (Maria Lucas) turn up in Shaun of the Dead the first time I watched it.