While the previous ruling party was bad, they did win 55% of the vote and that equaling the same number as a party who got 41% is ludicrous.
Tbf Samoan elections aren't exactly 100% free and fair. It's the typical goodies-and-clientelism* stuff rather than anything clearly undemocratic, but still.
And if a party loses the popular vote but wins government in a Western country with FPTP, nobody tries to prevent them from forming government. It's just that Samoa has a smaller electorate and more potential for freak outcomes like this.
* the latter is especially important; one of the reasons why HRPP has the ideology (if you can call it that) it has and why it has been able to stay in power so long is that Samoa is an extremely conservative country in the literal sense. There's deference to local bigwigs who have a lot of power in getting the vote out.