Edwin is a CONTRACTOR. William and Henry did not work for him, they worked WITH him. Fazbear Ent. and Fredbears Family Diner are entirely separate and successful companies. William and Henry did not "steal" his designs, they CONTRACTED him to help create prototypes of THEIR ideas. William and Henry thought of Springlock suits, Edwin designed and created prototypes which were to be finalized by William Afton and Henry Emily. Same with Freddy, Bonnie, Fredbear, and Spring Bonnie. William and Henry created the first drafts which were then passed onto Fiona and Edwin who created prototypes and designs which were to be approved by Willian and Henry.

  
WILLIAM AND HENRY DID NOT STEAL EDWIN'S DESIGNS. Edwin is a contractor who collaborated with Fazbear entertainment to help make prototypes and designs. Legally speaking, all of those assets created by Edwin Murray under the contract BELONGS to Fazbear ent, and therefore William Afton and Henry Emily. That includes any existing prototypes, blueprints, and plans. It is their property, to which they expanded upon. It's like contracting an artist to create art for an ad. If they were contracted to do so, that art is no longer theirs it is the company's.

  
William and Henry are still BRILLIANT INVENTORS. The Toy and Funtimes still exist, the Rockstars too. They built Fazbear Ent. AS A DUO WITH SOME HELP. All Edwin had were prototypes AND BLUEPRINTS (THAT BURNED UP ANYWAY) that were BUILT UPON AND IMPROVED BY AFTON AND EMILY.

  
TL;DR: William and Henr worked with him not for him, Everything Edwin made the prototypes FOR William and Henry, they didn't steal from him, William and Henry are still the origin point of the franchise.

  


Something I'm frustrated about people saying (Spoilers for SotM)