It was a short term solution to solve an institutional problem in the Boy Scouts. That problem being the decreased membership among young boys.

Instead of changing their program to attempt to better understand and accommodate the success of young boys, they instead opened up their membership to young girls, pretty much completely ignoring the problem facing their organization.

The problem has only continued to worsen, and more and more young boys continue to isolate themselves and drop out of society, because there aren't any programs or social institutions that represent their interests or even want to acknowledge they exist in the first place (let alone help them).

Girls being in the boy scouts was never the problem. The problem is that the girls were used to facilitate a foolish solution to a crisis that no one wants to even admit exists.