The introduction of the buzzword 'ajax' certainly popularized what people had already been doing for years though.
It's a shame the Microsoft engineers hadn't thought of making websockets instead. Bi-directional communication would have been useful for the web-based version of Outlook they were supporting, and it would have become available to the rest of us much earlier.
Remote Scripting itself was a copy of an IBM applet which Netscape pushed in the v4 timeframe (although practically, NS4 was too unstable to do any real dynamic html.)
So it really was the "AJAX" branding effort that got devs to notice what had been under their noses for some time.
("MSRS" now stands for something else entirely, but here's an old article discussing pre-historic AJAX techniques: http://www.ibm.com/developerworks/web/library/wa-resc/ )