Credit is absolutely due for using the monopoly distribution of Microsoft (that is not a slur, but it is simple truth that such components from other vendors could not have the same impact) to essentially sneak a simple HTTP ActiveX component through in the MSXML library, making such dynamic web tasks simpler. Credit is also due to the people who developed and implemented COM and ActiveX and safe-for-scripting (all heavily maligned), making it possible in the first place.
The component was developed by the Exchange 2000 team, and was integrated in MSXML as a convenient deployment tactic (the sort of thing that gets you in DOJ troubles) at the very last moment. I have no doubt that Bosworth valued it later, but if we're talking specifically about XmlHttp, it was in many ways snuck in because the Exchange team wanted functionality on the client.
