What should they have done? Fought alone or found other allies.

By the time of the Winter War Hitler had already been in power for six years. Nazi ideology was clear, as was ethnic cleansing of Jews in Germany and the countries annexed by then.

So although it is "easy" for me to make that statement at the top, it is also historically accurate that at the state level no hindsight was necessary.

I've never been a head of state/military making life and death decisions for my country, but I have run my own company for nearly 30 years. In that time I've turned down a lot of "cooperations" with companies where a possible short term advantage was clearly going to be a long term disadvantage or simply a "deal with the devil" - meaning there are countries I won't make contracts with, and business areas I won't bid on.

It is quite possible my company would be much bigger and I'd be retired in a villa somewhere if I had made such deals. I'd rather go to sleep every night knowing I wasn't making my money in a pact with evil. I also don't have to go to bed every night thinking I have as much to fear from my partners as I do from my competitors.