The idea of splitting school districts like Alpine School District wasn't random. Former teacher and state representative, David Cox, was serving as a stake (a stake is a collection of congregations - aka wards) clerk in The Church of Jesus Christ of Latter-day Saints in the 1990s when the growth in Lehi was just starting to take off. As clerk, his job was to divide up the congregations and change boundaries for the stake to split into two.
A lot of planning and considerations went into these decisions, and not every one was happy with them. Many people complained about how their ward boundaries were being redrawn. But the Church and its leaders knew that to accommodate the growth, they needed to divide, even though this would increase some expenses (duplication of services, offices, buildings, etc).
So why does the Church divide stakes? First, because it allows for many decisions to be made closer to the people. Second, it allows more people to be involved in their local wards and stakes. Additionally, when people become a number, lost in a sea of many, they are easier to become lost. To expound on a parable of Jesus, it's one thing to leave the 99 to go after the 1. If there were hundreds of sheep in a fold, there would be a lot more lost sheep and fewer shepherds. If the Church didn't divide their large congregations and stakes, it could not handle the growth it has experienced world-wide or even in Lehi, Eagle Mountain, and Saratoga Springs.
Recently, the Church of Jesus Christ of Latter-day Saints updated their handbook regarding creating new wards and stakes. As pointed out in a post by Matthew Watkins on X, the new recommendations align all countries and allow for smaller wards and stakes to be created in the US and Canada. There seems to be a sweet spot between too small and too big, as the numbers have increased for those outside US and Canada.
This sweet spot also exists for schools and school districts. Too large, and people become numbers. Too small, and things become difficult and very expensive to manage.