I don't know how that compares with Dota but you kind need to know what's the champions does to watch the tournaments

Same for Dota, but I've played both so in my case it's not really about knowledge. In Dota abilities have a bigger cooldown, often more wind-up, stuns are longer, the map is larger and abilities have more range which makes everything a lot more readable in my experience

And strategically it's day and night you have crazy tower dives 5 minutes in with 6 heroes, pros play ultra aggressively and every move is a clutch, it can be absolute cinema