"To cast a wide net" means to explore as many options as possible. It's a fishing metaphor. If you are fishing with a net, you will cast the net into the sea. You want your net to spread out as wide as possible into the water so that you can catch the most fish. In a business conversation about marketing, someone might say "we want to cast a wide net" to mean "we want to appeal to as many kinds of customers as possible." This would be the opposite of having a targeted campaign that focuses on a small group of customers. Or if you are looking for a job you might want to "cast a wide net" by sending your resume to lots of different companies. Again, the opposite would be to send your resume only to companies in a particular industry. The quote you put in your question is "cast as wide a net" and to me that sounds like part of a sentence. Perhaps they said something like "I would like to cast as wide a net as possible," or "Let's cast as wide a net as we can." Both of these are variations on the same "fishing net" metaphor.

To try many different things in order to find the one that works best. For example, if you were to look for a new employee you would use many different channels (multiple job search websites, News Paper ads, local classifieds etc) and by requesting applicants from people across a broad range of skills so that your message has further reach and appeals to more people rather than just placing a "help wanted" sign in your window