In LN the 'hero' decided the kingdom was going against the goddess' (basically human administrator's) will by seizing his conquest of the day and forced the king at swordpoint to give him an army to bring the country under his control and take her back. Excuse was since he's the goddess' chosen hero then he is always right, to go against him is evil and can be punishable by death, and a lot of other bs. Goddess took his side thinking of only the game and removed her 'blessing' on the kingdom. While not as bad as a curse, this caused turmoil as popular opinion wondered why goddess removed her favor, and all holy magic was greatly weakened due to priests etc. only being able to use their own power as they could no longer call on her for aide or power to their spells. As a result rather than use remnants of the summoning circle like in this manga, Giriel was able to use the now unclaimed and unmanaged kingdom territory to create a route to get to the human administrator. Don't remember exact details but basically needed to go directly from the world but because the world was completely under management of the administrators she couldn't get their permission to contact or approach them until human administrator removed the kingdom from her management giving Giriel an in. Also, in LN Giriel went into more detail about how the world was in bad shape partly because this was the only world where the administrators were refusing to communicate or read the head god's messages or warnings and was in danger of being condemned and destroyed as a result. Before heading out to rein in human administrator Giriel had watched the head god observe a world's final attempts to overthrow a summoned hero who was using modern machines and weapons to take over the world. Humanity and the demon king with his subordinates had tried to ally together but mounted knights were shot up with special machine gun bullets, the demon king's castle taken out with an ICBM, and all flyers shot down by Patriot missiles. So planet was destroyed.