Comment by Qem

Probably closer to the first situation. It curb stomped ArcGIS in the geographic information system community. When I started working with GIS at work, expensive ESRI products were default in this market, a la matlab in another field. Most coleages of mine had not heard about QGIS. Now QGIS is ubiquitous. It did to ArcGIS and its countless paid add on modules what scipy/numpy did to matlab.