This criticism is only valid if you can show that the due diligence team that worked Nokia also a) misreported the red flags / the enterprise value of the acqui

This criticism is only valid if you can show that the due diligence team that worked Nokia also a) misreported the red flags / the enterprise value of the acquisition, and b) were responsible for mismanaging the post-merger integration. A good deal of M&A goes ahead despite the warnings from the DD team. Sometimes it's a matter of CEO ego, sometimes a strategic long shot overruling the red flags.