The whole world didn't get involved in a war to kill or save the jews that is just ridiculous. Never happened, never was a thing.
In an essence it was more about England wanting to defeat Germany because Germany had surpassed them on the global market with superior production.
The Jews or rather the Rothschild's and their network of hundreds of stock exchanging Jews joined on the British side in exchange for Palestine.
Every nation had their own reason.
most nations liked Germany