How was XPCOM better than MS COM? Feature set? Nope. Tooling? Nope. Language support? Nope. Ecosystem? Nope. OLE components? Nope. Distributed COM? Nope. Doesn't trigger knee-jerk anti-Microsoft reactionaries even though it's a shallow clone of Microsoft technology? Check.
Did you know that "decomification" was a word?
https://bugzilla.mozilla.org/show_bug.cgi?id=194385