Bush and Obama did it too. Historically, it's been a targeted killing thing against Al-Qaeda (or so they have said), with whatever government they have, giving their blessing. If other sites are correct, Trump did it more, but it's kinda hard to pick nits there.
That's why a lot people are more upset over the lack of operational security than the action itself. They're not conducting themselves in a way that keeps our country safe, They skirting monitoring and can't even get that right.
There was no civil war in Yemen when GWB was in office. We attacked Al Qaeda in Yemen after Al Qaeda attacked the USS Cole in 2000. This is unrelated to any current conflict
The Yemeni civil war starts under Obama. The Houthis instigate the civil war.