Memory issues

[MaeseppTarvo]

Hey! I just wanted to know why does this loads every view all at once not only after tab click? It causes so much lag. I am pretty sure, this is library's fault. I am using it with Swift like this:

var tabBar: BATabBarController!

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    let tabBarItem1: BATabBarItem = {
        let tabBarItem = BATabBarItem(image: UIImage(named: "Tab")?.withRenderingMode(.alwaysTemplate), selectedImage: UIImage(named: "Tab"))
        tabBarItem?.tintColor = MainColors.mainLighterGray
        return tabBarItem!
    }()

    let tabBarItem2: BATabBarItem = {
        let tabBarItem = BATabBarItem(image: UIImage(named: "Tab")?.withRenderingMode(.alwaysTemplate), selectedImage: UIImage(named: "Tab"))
        tabBarItem?.tintColor = MainColors.mainLighterGray

        return tabBarItem!
    }()
    let tabBarItem3: BATabBarItem = {
        let tabBarItem = BATabBarItem(image: UIImage(named: "Tab")?.withRenderingMode(.alwaysTemplate), selectedImage: UIImage(named: "Tab"))
        tabBarItem?.tintColor = MainColors.mainLighterGray
        return tabBarItem!
    }()

    override func viewDidLayoutSubviews() {

        var vc1: UIViewController!
        var vc2: UIViewController!
        var vc3: UIViewController!

        let storyboard = UIStoryboard(name: "Main", bundle: nil)

        vc1 = storyboard.instantiateViewController(withIdentifier: "Tab1")
        vc2 = storyboard.instantiateViewController(withIdentifier: "Tab2")
        vc3 = storyboard.instantiateViewController(withIdentifier: "Tab3")

        self.tabBar = BATabBarController()
        self.tabBar.tabBarItemStrokeColor = UIColor("#3F72AF")
        self.tabBar.viewControllers = [vc1, vc2, vc3]
        self.tabBar.tabBarItems = [tabBarItem1, tabBarItem2, tabBarItem3]
        self.tabBar.setSelectedView(vc1, animated: false)

        self.tabBar.tabBarBackgroundColor = MainColors.mainDarkerGray
        self.tabBar.delegate = self
        self.view.addSubview(self.tabBar.view)

    }

    func tabBarController(_ tabBarController: BATabBarController!, didSelect viewController: UIViewController!) {
        print(viewController)
    }