Probate litigation isn't something that most people will experience in their lifetime. Most wills go through the process without any issue. In fact only around 1 percent have issues, while the remaining 99 percent pass though without any problems.
You can't challenge a will for any random reason, nor can anyone contest it. There are very strict requirements for doing this. You have to be a person with a valid interest in the will, which means that you are actually in the current will, in a previous version of it or would stand to inherit something if there wasn't a will at all. If none of these apply, you can't contest the will.
There are specific cases that qualify for a will contest. If the person who created the will didn't have testamentary capacity when it was written, you can contest. This means that the person wasn't at least 18 years old when they signed the will. Other reasons have to do with not understanding specific points about the distribution of assets or points about the heirs and beneficiaries.
In some cases, the reason to challenge a will is that there is a newer one that has been found. The court will look at the dates of the wills to determine which one is the most recent. Since people can update wills if and when they see fit, the most recent one must always be the one that is followed.
There are often other points that make challenging a will difficult. In many cases, the person who is challenging it is going up against family members, which can change the dynamics of the relationship. It is imperative that all of this is considered before any action is taken.