I would have thought that his public articles regarding military planning and needs would have been enough. This information was sensitive. Though those articles had a lot of truth to them... this nature of war has changed so we failed was a a bit CYA too.
There were many other factors too. First offense is a lot harder and Ukaininan army unlikely has the skills for large scale maneuver warefare. Secondly, they wasted a lot of their force across the front and did not concentrate on a single direction. The west has been a day late and a dollar short on supplies as well. They do not have air superiority and long range attack weapons too. The constraints the West puts on ukraine... no use of our weapons on Russian territory is absurd. Finally Ukrainian society not moving to full mobalization is nuts.
Edit: Also lack of political clarity in the West has been a huge issue.