A lot of the ancient Kingdom wars weren’t meant to embroil the whole realm. They started off as battles between opposing groups - often a village plagued by the antics of boisterous sprites would call in a wizard or two. They’d deal with the problem initially (sprites died, this was always considered a good idea by anyone not a sprite) but then would follow the inevitable quarrels as to who succeeded the most and deserved the most credit (and rewarding gifts) from the monarch. Even when the villages were foresighted enough to only call in one wizard, there were cases of power going to the head and the wizard going beyond the terms of his commission. The village would then need to call in someone more powerful to stop him. There isn’t a village in the realm not affected by this somewhere in the past.
There isn’t a military in the magical realm. All fairies are meant to be “good”, most wizards are as are some witches (the ones who stick to studying herbs and their healing properties as opposed to those who like shoving kids in an oven. It’s so vital to be able to tell which witch is which!). Some wizards have been known to develop spells that can be used as weapons and seek to sell them to the highest bidder. The fairy government gets around this problem by making sure they are the highest bidder. They then usually arrest the wizard trying this scheme!
Because so many wizards went over to the dark side in the olden days, the fairy royals instituted a new idea where the best wizards would compete in a competition held once a year to show who was the most powerful. The wizards took part for the prestige of winning a magically sponsored competition. The fairy royals got to see who was the most ambitious new wizard rising through the ranks. They could and did then take steps to ensure these wizards only worked for them - it’s not just the Chief Witch who thinks blackmail is a phenomenally useful tool!
The Queen’s and Eileen’s family have had their own fair of trouble where contenders for the throne vied for it. Still as the records show this was always sorted out - someone inconvenient died. The Queen herself inherited her throne thanks to the murder of her mother by the Chief Witch in revenge for slights on her family and the fact the Queen’s mother killed the Witch’s one. This was done in self defence but there was no way the Witch was going to accept that “excuse”. There have been some, half hearted calls to turn the realm into a republic on the basis that there wouldn’t be fighting for the throne if you took the throne away. But what’s gone against this have been the numbers of good monarchs have outweighed the bad ones, the Kingdom likes its traditions, and nobody wanted to see the spectacle of presidential contenders vying for votes. The realm has seen this happen on Earth and think it distasteful and lacking in dignity.