We obviously don't know like 99.9% of the full story, but the fact that he had a long session with the COO one evening and then got fired the very next day in the morning is just plain evil and wrong. It's not how you treat a human. It's disrespectful to say the least. The employee went home feeling good, so the COO basically charmed him up the day before firing him in order to get out the last ounce of what they considered was worth getting out of this employee before discarding him. That's disgusting behaviour and I personally would never want to work with such a COO or company at all.
Now on the topic of swagger. I agree, it's important to know who you are and be comfortable to be that person. Every human contributes in their own way. Swagger doesn't mean ego or arrogance, to me swagger means you know your strengths and feel comfortable to play your role in your team/community/family/etc.
Some people are great critical thinkers, some are great motivators, jokers, conservatives and risk averse planners, etc.
You need all of them. Everyone has their own swagger. Some people are quiet and sit in the corner of a room and throw in a critical question at the right moment of a meeting which others might find annoying but in the end everyone knows it was good that it happened. Some talk a lot, walk into a room and make jokes and struggle to sometimes focus on the topic at hand but they lift up spirits and soften the mood when things get heated. Like there is really no perfect human being. You need all those different characters to contribute and it requires everyone to be accepting of the other person in order to really become a great team. This is how it works in strong families who go through thick and thin and this is how it works in great performing teams.
Know yourself and know your swagger!