Why is Evertale act 1 and other acts so different?

Evertale act 1 was really good. You can roam around freely. You can also capture monster units. But in online story it just fells a bit like a minigame and you need mana to fight. Why?

Sadly, almost all mobile games use a mana system that replenishes over time. It’s proven an effective method to get people logging in regularly and sticking around to play the game in the long run. Act 1 is to draw you in and give you a decent amount of content to play. It’s just enough to get you hooked and stick around for what is actually the main content of the game.