Kaidus always knew the teams and players he casted. Either because he'd been scrimming against them for years or they were his own teams. This resulted in every match being very accurate in terms of explaining what the teams are looking for. Often accurately predicting the plays if he was familiar enough with the teams.
It made for educational casts for learning the mindset of EU TF2 but also learning about individual tendencies/play styles. A lot of players had their own personality in-game and Kaidus could be scarily familiar with it.
Also the occasional small bm when someone he knew fed was entertaining. Like a mildly disappointed dad.
Watching b4nny cast NA matches probably gives similar vibes for NA players
Had he casted ESEA/OZF matches I don't know if his casting would've been at the same level as he was less familiar with those teams/metas. No doubt it would've been very insightful still, but a big part of what made his casting so great is how well he knew the teams.
For me, an EU player trying to learn to call more, Kaidus was the perfect caster (at the time)