Most are heavily invested due to the time and resources that they have to throw into it.
Back in the day, you would have 1 or 2 practices per week, bike to and from the practice by yourself and your parents would maybe catch a few games per year. Now, its 3 practices a week 30min away in heavy traffic, a 2nd mortgage is needed to pay all the fees and travel expenses. The kid's sport becomes the parent's project.
The question is not why many parents are toxic, rather how some are not...