Why should every software company manager study digital marketing?

This image is from pixabay site I have been working as a software engineer for almost 7 years. 2 years ago, I had a new software idea that I thought people would love it. I spent over 1 year developing this software and finally I launched it a few months ago. The software is a competitor to a famous software company that has more than 50K  customers.  The application has a free version to encourage people to install it and I thought it is enough for marketing the application but the application now has been launched over 6 months ago and only 100 people have installed it. As a software engineer, we focus on building the apps with creative ideas but we don't have any idea about how to market it. I started to ask myself how this software can gain much more visibility. How can people know about it more? Promoting on Facebook, Twitter or LinkedIn? Hiring a motion graphics agency to have a nice video for the application? Focusing on SEO? What's the most important thing should I foc