Why has Fortran programming language almost disappeared whereas COBOL still widely used?

Answer 1

FORTRAN was more accepted for scientific applications which tended to have relatively short lifespans. As time passed, new development had other more recent and robust languages available for use.

COBOL otoh was widely adopted for business applications that would continue in use for years or even longer. For example, at the time of Y2K bug concerns in the late 90s, programs were being modified that had been in use for decades - some since the 60s. The massive number of programs involved made considering a rewrite in another language on top of addressing the Y2K issue impossible for most companies.