which Technology Stack is currently used in leading Software companies for web app and WHY?

what is the trend in Software companies now? Which Technology does most Software companies use currently? Does it depend on the need and backward-compatibility to support existing apps? My team is currently planning to shift from java to C# for a various reasons. Is there a better alternative and WHY? They are also considering ReactJS for front end. How good is that? Is there any better alternative for it? Ease of development, Ease of maintenance, Extensibility, Dynamic web development, Scalability, Security are some of the factors i'd like to consider.