I am confused why they are around to begin with.

Companies already trust Microsoft, they buy Windows, Office, Azure.

Why would they bother with a 3rd party here when the low effort low risk solution is to pick the tool made by the OS vendor. I.e. windows defender

It should be a nobody gets fired for picking IBM situation. How did this random place get so much credibility that people trust them over the manufacturer?

crowdstrike has oracle enterprise sales model. have you ever been to one of their events?

Because they provide far more protection than Windows defender. You can write your own custom never-before-seen malware, and CrowdStrike will detect it purely based on behavioral signals. Windows Defender is still largely an antivirus solution.

Microsoft's E5 offerings are a direct competitor to Cloudstrikes threat response products which is a lot more than just Windows Defender on endpoints. I'd imagine many of Cloudstrikes customers will be looking to move this to MS's tools instead as a result of this.

You don’t drop them until budget renewals, at least not for this. Solarwinds comes to mind as a company with a similar kind of thing.