well, there was no intention from Nato´s side to let them in as a partner, and those reasons is many and complex, as well there was no intention to feed them wit high tech weapons either, because of unstability, corruption, priveate armies. Cia had a long report on the critical issues, and why Ombama did not feed them with weapons, which Donald easily overooked.
The war would eventiually happenend no matter which president, and Crimea is an important strategic island for Russia for their shipping as well strategic for military reasons.