The USA has a long (perhaps entire) history of putting itself first:
It also has a history of putting dictators in power. And, it has a history of abandoning support when it suits them.
Why would it be any different now?
It wouldn't. I don't think that the world should "rely" on the US at all.
I don't think is anti-war though. I think he recognises how valuable war is, but also that it loses some value if US has to directly get involved. WW2 was them selling to both sides as well, until Pearl Harbour.
Right yeah - I despise that we in Europe have left our military to rot for so long by relying on the collective strength, that the UK for example by itself can barely stand on its own two feet. We all come crying to the USA about everything it's absurd.
Trump ultimately is a businessman to the bone. I don't believe anything he says is based on a deep morality, but on how he can turn it to an advantage - this is true.
War, to him, gives China a big advantage on many levels. That, I reckon, is the ultimate crux. Although I'm no military strategist so just a guess really!
Ultimately though, ending the death is still priority number 1. The rest can be worked out later