FORTRAN 77 is far more popular because it took so long for a GNU FORTRAN 9x compiler to appear, and meanwhile there are millions of lines of FORTRAN 77 in enormous libraries.
The problem with the standard library is that it is tiny and its basic types are often ill designed. Certainly it's fairly consistent, and so fairly unsurprising, but that's not the argument.
It also has to do with the type of people that program in FORTRAN. They often have backgrounds more grounded in Maths or Physics than computers. I don't think the GNU compiler had much to do with it because people using FORTRAN are more likely to be using something else (we use Solaris Studio where I work).
The problem with the standard library is that it is tiny and its basic types are often ill designed. Certainly it's fairly consistent, and so fairly unsurprising, but that's not the argument.