I was typing that on a phone and didn't have time to elaborate. IE was only popular when IE 6 was light years ahead of Netscape 4.7 in 2001. Netscape 5 and 6 I did not even bother as websites would not even render correctly. Not because the IE era started on the web, but because there were more quirks in thsoe pieces of dinosaur doo than even IE itself!
People use what is best. IE no longer has the strangle hold because it is not the best thing since sliced bread anymore.
In 2001 through 2003 I used it with Mozilla, but not since Firefox .9x did I finally feel a worthy competitor came.
By 2004 it was an insecure old awkward browser but not terrible. By 2006 it was a POS HORRIBLE abomination! This is when average Joes started using alternative browsers as techies told them to use Firefox.
MSE now is going bad and I no longer use it just like I no longer use IE unless I am at work. People use what is best and yes a good 20% are sheep but the rest will find something else.
I think MSE came about just like IE (since analogy was brought up) as a better alternative as everything else sucked worse. Norton was worse than the actual damn virus! Symentec same ... McCrappy just as bad. AVG would work and then corrupt your Windows installation, etc.
Now Norton is re-engineered and is a great lightweight and secure again though geeks wont touch it now. Avast is much better and we have Avirri and Panda which are ok and fairly decent for free or low cost.
MSE is ... well old. It is scanner from an older era that does not have the whistles of active protection and sandboxing. Just like IE it became an abomination as it never was great (just sucked less) and became out of date where everyone is going one way, MS is staying put in technology.