Rather, Russia has 170 million people including a certain number who are not ethnically Russian and may or may not identify with Russian goals. For example, some of their natural gas provinces are in Muslim provinces. The local populations might not be supportive if Putin not only wants to strong arm fellow Muslims in Crimea, but also cuts of their source of revenue.
As a side note, Putins claims that Russians are in the majority in Crimea are based on a census that is ten years old and did not count the continued influx of pro Ukrainian Tatars. Western oriented Ukrainians can even call out crowds in Kharkov / Kharkiy which is in far east Urkraine. And... the Ukrainian admiral who defected has gone to Ukrainian bases trying to get more Ukrainians to join him and has been flatly turned down.
Though there are probably millions of wildly pro Russian Ukrainians, my guess is that the total number is substantially less than 50% of the population.