The power of transnational corporations is enormous. Corporations have limitless amounts of money that they can spend as they wish. They can use this money to invest, to conduct research, and to buy influence. Buying influence = bribery.
If a country has certain laws that a certain corporation does not like, it can use money, gifts and travel to influence politicians and people in power.
That influence can change laws or talk rulers into allowing corporations to do what they want to do.