wpf 样式问题

今天看书时发现一个问题，觉得有点意思就做了一个demo：

 <Window.Resources>
        <Style x:Key="BigFontButtonStyle">
            <Setter Property="Control.FontFamily" Value="Times New Roman"></Setter>
            <Setter Property="Control.FontSize" Value="18"></Setter>
            <Setter Property="Control.FontWeight" Value="Bold"></Setter>
        </Style>
        
        <Style x:Key="ButtonStyle">
            <Setter Property="Button.FontFamily" Value="Times New Roman"></Setter>
            <Setter Property="Button.FontSize" Value="18"></Setter>
            <Setter Property="Button.FontWeight" Value="Bold"></Setter>
        </Style>
        
        <Style x:Key="TargetTypeStyle" TargetType="Button">
            <Setter Property="Button.FontFamily" Value="Times New Roman"></Setter>
            <Setter Property="Button.FontSize" Value="18"></Setter>
            <Setter Property="Button.FontWeight" Value="Bold"></Setter>
        </Style>
    </Window.Resources>
    
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>
        <Button Content="Control.FontWeight" HorizontalAlignment="Center" Name="button1" 
                VerticalAlignment="Center" Style="{StaticResource BigFontButtonStyle}" />
        <TextBox Grid.Column="1" HorizontalAlignment="Center" Name="textBox1" 
                 VerticalAlignment="Center" Style="{StaticResource BigFontButtonStyle}" Text="样式有效" />
        <Button Content="Button.FontWeight" Grid.Row="1" HorizontalAlignment="Center" Name="button2" 
                VerticalAlignment="Center" Style="{StaticResource ButtonStyle}" />
        <TextBox Grid.Column="1" Grid.Row="1" HorizontalAlignment="Center" Name="textBox2" 
                 VerticalAlignment="Center" Style="{StaticResource ButtonStyle}" Text="样式无效"/>
        <Button Content="TargetTypeStyle" Grid.Row="2" HorizontalAlignment="Center" Name="button3" 
                VerticalAlignment="Center" Style="{StaticResource TargetTypeStyle}" />
        <TextBox Grid.Column="1" Grid.Row="2" HorizontalAlignment="Center" Name="textBox3" 
                 VerticalAlignment="Center" Text="没有效果" />
    </Grid>

如图效果：

第二排textbox设置的是button的样式： <Style x:Key="ButtonStyle">
<Setter Property="Button.FontFamily" Value="Times New Roman"></Setter>
<Setter Property="Button.FontSize" Value="18"></Setter>
<Setter Property="Button.FontWeight" Value="Bold"></Setter>
</Style>应该是无效，怎么还是有效呢？