They were in the market early and profit from some "nice" lock-in effects. They have excellent relations with many large companies who tend to require that their suppliers use SAP.
The automotive industry is notorious for this but I also know of some small companies that were essentially forced to use SAP to even compete for contracts from some big companies (Bosch comes to mind)
ABAP is also fairly "consultant friendly" and extremly backwards compatible. Sometimes I jokingly call it the new Cobol. If you ever think "man my language of choice is pretty kludgy" feel free to look at some ABAP code/docs and you'll feel a lot better :P
If by "generally works and at a very, very large scale" you mean it's slow as molasses no matter how many or how few users there are, and you're unable to provide a decent user experience, than I have to agree. Otherwise, I'd say "feels kinda clunky" is a stiff-upper-lip kind of understatement.
I'm not sure I can agree with this.
Back in 2001, before I discovered the California bay area start-up scene, I worked in a very large telecommunications company that everyone has heard of. SAP seemed pretty good; albeit hard to master.
>100lb gorilla
Seems fairly...light.