If you define "believe in" as "thinking they were doing something amazing and world-changing," sure. If you mean it in the more normal sense of "Think it is a w

If you define "believe in" as "thinking they were doing something amazing and world-changing," sure. If you mean it in the more normal sense of "Think it is a worthwhile endeavor that has a reasonable chance of success," the distinction you're drawing here doesn't seem very salient.