Because they're not really obsessed with "America First". It's just the cover they use to excuse not giving a damn about "others". They don't care that others are dying. They just care about being able to do what they want to do without restriction. Also, they think politics is a team sport and will excuse anything their side does so long as it's at the expense of the "others". There are some on the left guilty of this too, of course, but it's practically a requirement for Trump supporters.