Your point about more care during the merger is very true. However, just because antitrust regulators think it will be ok doesn't mean they can't change their

Your point about more care during the merger is very true. However, just because antitrust regulators think it will be ok doesn't mean they can't change their mind. If it did, then breaking up monopolies would be impossible. Consistency in the law is critical (current US administration demonstrates this), but the economy is dynamic, and consistent principles ("no monopolies") are completely fine, and may give different results when applied to the same entities at different times.