Galaxy
They polled badly for numerous reasons, politics is rarely down to one factor, they massively misjudged how people feel about overthrowing a democratic vote, they could have managed that in a much more voter friendly way, jo Swinson was not effective, they became mired in identity politics, they alienated some women, I could go on.
The Liberal Democrats had one continuous message during the General Election campaign and that was NO BREXIT, NO BREXIT, NO BREXIT
Labour Party support was totally divided with the North of England heavily supporting Brexit while the South of England were heavily in support or Remain. The Labour leadership tried to bridge that gap with a confused and difficult message.
Boris Johnson had one continuous message during the General Election campaign and that was BREXIT, BREXIT, BREXIT.
Under Britains first passed the post electoral system the voters went overwhelmingly for the Boris Johnson message.
Simple as that.