Why does not the form validate the fields?

/**
	 * Funcao para verificar se é para alterar funcionario a partir da persisitnecia do id
	 */
	$scope.enableChangePassword = function() {
		console.log("verificando se é para alterar funcionario");
		list  = document.getElementsByClassName("iptPass");
		if ($scope.meuUsuario.getId() != '') {
			document.getElementById("checkbox").style.display="block";
			document.getElementById("PassBox").className += "col-md-12";	
			for (index = 0; index < list.length; ++index) {
				list[index].style.display="none";
			}
			console.log($scope.meuUsuario.getId() != '');  
		}else {
			document.getElementById("checkbox").style.display="none";
			for (index = 0; index < list.length; ++index) {
				list[index].setAttribute("required","");
			}
		}
	}
	
	$scope.init = function (){
		$scope.enableChangePassword();
	}
	
	$scope.init();

<div class="tabs-container" ng-controller="GetMoreUserController">
<div ng-include="cadUsuariosTab.url"></div>
<div ng-init="tab=2">
<div class="wizard-container" ng-init="quad=1">
    <div class="card wizard-card ct-wizard-red">
    <br>
        <ul class="nav nav-pills" role="tablist">
            <li role="">
                <a aria-controls="Dados do Titulo" role="tab" data-toggle="tab" ng-click="quad=1" ng-class="{'active' : quad==1}">
                    Dados Básicos
                </a>
            </li>
            <li role="">
                <a aria-controls="Pesquisa" role="tab" data-toggle="tab" aria-label="Toggle" ng-click="quad=2" ng-class="{'active' : quad==2}">
                    Dados Complementares
                </a>
            </li>
        </ul>
    </div>
    <div class="tabs-container" ng-controller="CadUserController">
    	<br>
        <form id="formCadUser" ng-init="carregarUsuarioAlteracao()" name="formCadUser" class="col-md-8" ng-submit="">
            <div class="tab-content" ng-show="quad == 1">

                <div class="col-md-6 form-group">
                    <label for="nome">Nome</label>
                    <input id="nome" name="nome" type="text" class="form-control" ng-model="caduser.nome" ng-minlength="2" required>
                </div>
                <div class="col-md-6 form-group">
                    <label for="sobrenome">Sobrenome</label>
                    <input name="sobrenome" type="text" class="form-control" ng-model="caduser.sobrenome" ng-minlength="2" required>
                </div>
                <div class="col-md-12 form-group">
                    <label for="username">Username</label>
                    <input id="login" name="username" type="text" class="form-control" ng-model="caduser.login" ng-minlength="2" required>
                </div>
                <div class="col-md-12 form-group">
                    <label for="email">Email</label>
                    <input name="email" type="email" class="form-control" ng-model="caduser.email" ng-minlength="6" required>
                </div>
                <div id="PassBox">
               		<div id="checkbox"><label><input id="cb" type="checkbox"> Alterar Senha</label></div>
	                <div class="col-md-6 form-group iptPass">
	                    <label for="senha">Senha</label>
	                    <input name="senha" type="password" class="form-control" ng-change="clearAlert()" ng-model="caduser.senha" ng-minlength="4" >
	                </div>
	                <div class="col-md-6 form-group iptPass">
	                    <label for="senha">Confirme a Senha</label>
	                    <input name="confSenha" type="password" class="form-control" ng-change="clearAlert()"  ng-model="caduser.confSenha" ng-minlength="4" >
	                </div>
				</div>
				
            </div>
            <div class="tab-content" ng-show="quad == 2">
                <div class="col-md-6 form-group">
                    <label for="senha">Campo Qualquer</label>
                    <input name="" type="text" class="form-control">
                </div>
            </div>

            <div class="container-fluid form-group">
                <div class="col-md-4 pull-right">
                    <br/>
                    <div>
                        <!--<button type="submit" name="submit" class="btn btn-default pull-right col-md-6" ng-click="cadastrarUsuario()" ng-disabled="formCadUser.$invalid"> -->
                        <button type="submit" name="submit" class="btn btn-default pull-right col-md-6"  ng-click="cadastrarUsuario()" ng-disabled="formCadUser.$invalid">
                            Cadastrar
                            <span class="glyphicon glyphicon-ok-circle"></span>
                        </button>
                        <button type="reset" value="" name="clear" class="btn btn-default pull-left col-md-5" >
                            Limpar
                            <span class="glyphicon glyphicon-remove-circle"></span>
                        </button> 
                    </div>
                </div>
            </div>
            <div id="alerta"></div>
            <hr>
        </form>
    </div>
    </div>
   </div>
</div>