Why did RCA, Westinghouse and companies like them initially choose to venture into broadcasting?

They had realized that with the success of the Film, there was a n increasing need for people to get broadcasting.

Explanation:

The developments in the 1930 era US meant that the people were acquainted to cinema and there were cartoons being made and music was being commercialized too.

So the companies realized that Broadcasting could turn a great source of profit from the wealthy individuals who could afford to keep such TVs in their houses.

Thus many companies began to broadcast in 30s when the first cartoons were being made at Disney and soon TV broadcast took over as a major form of entertainment.