You answered your own question. The penniless refugees definitely endured a lot more conditioning and had the need to grasp more skills quickly than their Irish counterparts.
Do you think being outsiders actually helps then? Jews in most countries, Ugandan Asians in the UK, Chinese in the Philippines and Indonesia are all examples of small outsider communities with huge commercial success. Perhaps having a second nationality/identity and a sense of being under siege is part of what's needed?
Actually, that probably plays a significant role. When you're culturally different than the country you immigrate to, you're less self conscious of what role you play, and can do what's necessary to be productive, even if demeaning. The more you're like the culture of the country you're immigrating to, the more energy you probably expend trying to maintain the facade of already being part of that culture, and as a result, the less productive you can be.
To put in further perspective, the immigrating culture that is different is more likely to band together, and support each other in participating in the demeaning tasks, build a better network, and be more successful at building a business through their network.