“The FBI, not Crowdstrike, should have examined the DNC computers.”
to at least avoid the appearance of impropriety...
Also, to do a thorough, professional, independent investigation.
But the DNC did not want a thorough, professional, independent investigation. They needed a scapegoat, someone to blame for their hugely embarrassing campaign failures. Therefore, they hired Crowdstrike, and Crowdstrike gave them the scapegoat they needed: THE RUSSIANS HACKED THE ELECTION!
Given the circumstances, there is no reason to believe any of Crowdstrike's claims of Russian hacking.