<table>
<thead></thead>
<tbody>
<tr><td>1</td></tr>
<tr><td>2</td></tr>
<tr><td>3</td></tr>
<tr><td>4</td></tr>
<tr><td>5</td></tr>
</tbody>
</table>
document.querySelectorAll('tbody > tr').forEach(n => n.parentNode.prepend(n));
// или
const tbody = document.querySelector('tbody');
tbody.append(...Array.from(tbody.children).reverse());
// или
for (const n of [...document.querySelector('tbody').rows].reverse()) {
n.parentNode.appendChild(n);
}
// или
const tbody = document.querySelector('tbody');
for (let i = tbody.rows.length; i--;) {
tbody.insertAdjacentElement('beforeend', tbody.rows[i]);
}