Are Polish people Stoics? My observation is yes. Considering my ex who organizes one of the most grueling races of all time "Bieg Rzeznik", 50 miles race for best time in the Bieszczady Mountains. If interested, you can check out the race online.
Back to the question. First, what does it mean to be a Stoic. Maybe we need to look at Epicureans to better set up for Stoicism. Epicureans aim at being happy "don't worry be happy", que sera sera (sorry on the spelling) you know "what will be will be". You only live once!
The Stoic is someone who sees/thinks the divine is in all things and because of that enormous complexity, the creator, what is divine, is unknowable. All we can do in this world is dig in and make it to the other side but even that is not for sure. So why bother. The Stoic is sure about a divine spirit in all things, therefore, it is ones duty/religion to do something... the will to do something. Even Thorstein Veblen saw that in his observations. No matter what the challenge, just do it, you have to, the divine spark in you should not be wasted! Niki must think so, it got them to a market position that may never be toppled.
Is that a good thing? Paul spoke in Athens to people of these two schools of thought. He appealed to them both. I myself am a bit of a Stoic. God is there, no doubt and his will should be mine. Sometimes I think that I will never know what that is unless I go the distance. Guess my Polish roots go deep like the runners of Rzeznik.