SQL Server 2000 was well received in the segments that mattered as a challenger. Oracle was in first place running on Unix. However, it was viewed as expensive and the procurement experience was regarded as unpleasant. People wanted competition even if they didn't think SQL Server, or another alternative, could unseat Oracle for the most important stuff.

Windows was really picking up steam and there was a move to web development in the Windows-based developer space. Visual Basic and Delphi were popular but desktop development had peaked. ASP was for building your apps and SQL Server was the natural backend. SQL Server fed off this wave. It wasn't dislodging Oracle, but rather than every app being built on Oracle, more apps started to use SQL Server as the backend.

Then ASP.NET appeared on the scene and demand grew even more. It was a well-integrated combo that appealed to a lot of shops. I started my career in a global pharma and there was a split between tech budget. IT was a Windows shop for many reasons and ran as much on SQL Server as possible. R&D was Unix/Linux with Oracle. There was a real battle going on in the .NET vs Java (how about some EJB 1) and the databases followed the growth curves of both rather than competing against each other.

The SQL Slammer worm brought a lot of attention to the product. There were instances running everywhere and IT didn't expect so much adoption. Back then you had a lot more servers running inside offices than you do today. My office was much like my homelab today. This validated the need so the patches got applies, IT got involved in the upkeep, and adoption continued to grow.

Oracle's sales folk and lawyers were horrible to deal with. I had some experience of this directly as they tried pushing Java-related products and my boss dragged me into the evals. One of my in-laws was outside counsel in the IT space doing work with enterprise-sized companies. He claims they are the worst company he's ever had to deal with and wouldn't delegate any decision-making locally which endlessly dragged out deals. They had a good product but felt they could get away with anything. Over time he saw customers run lots of taskforces to chip away Oracle usage. This accelerated with SaaS because you could eliminate the app AND Oracle in one swoop.