I understand most acts used the in-ear monitors which were working okay, but Jemini, the British act, opted for the stage monitors which weren't up to the job. Presumably they were okay during rehearsal before crowd noise was added in.

Anybody, even in the folkie world, would sympathise with any act in any musical genre where they can't hear what they're singing.

But, as has been pointed out above, it doesn't excuse the song, the arrangement, or that dress