I don’t think the majority favored big business. They simply applied the law Congress passed. The court even implied that they might not think the contracts are fair, only that it is the law.
And this isn’t bad for employees, either. If they have a solid case, an attorney will take it on contingency, or a large group can fund the expense associated with arbitration, which is far lower than going to court. If they win in arbitration, they get all the money due to them and the employer pays their legal fees.
There are arbitration agreements between companies in separate countries that have potentially billions at stake, so it’s not like arbitration provisions are only to screw over the little guy.
Wow, interpreting the law. What a novel concept...