I'm sure many made the same argument in 1986 that the new ST was not going to work simply because it didn't have any of the original cast, characters in TOS and the movies. They were wrong.
1) Trek had been off TV for 20 years.
2) They did and they were right in the end. It wasn't till Berman took over and made TNG into what we commonly think of TNG Trek that it took off. Even then by the time DS9 rolled around the numbers dropping off. DS9 was a entirely different creature and when they went back to Traditional Trek it struggled for years till it was put out its misery. TNG was a success cause of the novelty of it, the novelty had wore off. Look at were we're at now: Kirk and Spock back on the big screen, making bank.
3) Different television market and less competition against television in general