My question is, when did this fact become clear? In my experience there was not a specific year. Smaller businesses started requesting Linux in the early 00's

My question is, when did this fact become clear? In my experience there was not a specific year. Smaller businesses started requesting Linux in the early 00's and the popularity started working its way in with bigger companies. With time more Linux monitoring tools were being developed and that really helped the adoption as customers had SLA requirements that required standardized monitoring tools. More high availability tools and daemons also started being ported from BSD which also helped adoption. More and more enterprise capabilities meant more customers requested it. Eventually our customers had enough developers using Linux that it was just expected to be an option. There was more to it but this would turn into a book. Oh but I should add one important driver ... cost. HP-UX, AIX were insanely expensive and Linux was free to our customers since we had a lot of Linux experience in house. Commodity hardware was significantly more cost effective if apps could scale horizontally. Solaris and Windows held a position for some time and then after Oracle roflstomped Solaris it was just Linux and Windows by the time I left that company. This was when commodity hardware and horizontal scaling become more common. Everything I described mostly transitioned from around 2000 to 2003.