He made no real effort to resist and did nothing to sell Isabel as his heir to the people. Pedro II was pretty popular when he was deposed, he could have resisted or prevented it if he wanted to but he didn't fight it at all.
If Italy-German relations go through a different route than IOTL in the 1930s, would it be plausible to say that Mussolini-led Italy can join the Allies?
The United Kingdom created the Stresa Front with France and Italy to help contain Germany. Two months later the Anglo-German Naval Agreement was signed without the consultation of France and Italy, which caused Mussolini to decide that Germany couldn't be stopped and he had nothing to lose by invading Ethiopia.
While we're on the subject of WWII neutrals joining the Allies, if Ireland did, how many (British and later American-equipped) units could be squeezed out of it?
Ireland wouldn't join the allies, especially as the prime minister of Northern Ireland at the time of WWII called on Churchill to have the British Army invade Ireland.
At the most like in history, joint plans between Ireland and Britain such as Plan W would be made if the German's invaded Ireland.