How do i place same widgets multiple time by default on theme activation?

Question

You’re quite off with your code. That’s not how widgets are stored (at least not since 2.8), plus you’re trying to inject arrays into strings!

Setting default widgets (at least in the admin) seems a complex & messy task. I would much rather opt for default widgets in the display logic instead.

<?php if ( ! dynamic_sidebar( 'primary-sidebar' ) ) : ?>

    <div class="widget">
        My default widgets!
    </div>

<?php endif ?>

The content within the if statement will print if no widgets have been configured, which will be the case on initial theme activation.