Every business decision that fails or succeeds is a management decision...
Business decisions aren't like making Cisco's business critical applications like "flashlight" for the Cius where the competent can know with 100% certainty that the application will work before they start. Senior management at all companies have to make wild-a55 guesses and if Cisco's competitors were much better at this they wouldn't still be collectively dwarfed by Cisco.
If you ever worked in an environment that demands fixed price and fixed time you learn how to figure out what you're going to do and how you're going to do it and you have to be confident the problem is doable within the time and money available or you pass. Cisco's engineering staff has no experience with any of this and I can point to technical decisions at relatively low levels that have cost the company tens of millions each and delayed critical projects by years each.
"Oh, management let them be fools!" Yes, management who were those very fools only a few years before when they were bad minions.
"Oh, just hire better people!" Like the best of the best want to maintain 40 year old COBOL in a more than 50 year old language.
On the cloud, there was a big move to white box compute and networking to reduce costs, things Cisco doesn't know how to do. What critical piece would Cisco have brought to the table to starve off competitors when cloud took off? Read only SNMP for management? Boxes which could never be rebooted because a single reboot breaks five nines over the course of an entire year? The need to roll a truck when software on a single component in a box fails?
The other also-ran legacy players who made a serious effort are bit players with 5% of the cloud market combined and they had compute and data experience Cisco did not. Cisco never had the technology nor the culture to take on this market and given the players that won Cisco had no way to acquire their way into this market. It's far more complex than asserting "they should have just made the right decision."