[Endoperez]

At Easy difficulty, the AI gets resource and gold PENALTIES.

MA Ulm starts with a good fortress (good admin -> more resources), tends to start in or near mountainous provinces (more resources) and gets extra resources in all of its forts as a nation-wide bonus. Their national units are very cheap on gold. It probably got lucky and the pretender had scales that fitted the nation, and the capital was surrounded by high-resource provinces.

In addition, while it's not cheating per se, the AI is way more efficient at recruiting from independent provinces than any human player. It can recruit from all provinces it has conquered, every turn. Most of those units are useless, so once you learn how to take care of chaff the number of units doesn't matter any more, and that's when you up the AI difficulty and/or use mods/maps with AI-friendly features.