>>> it definitely is kefirah to think that the fate of the jewish people depends on the bechirah of goyim.
Claiming that believing that goyim have the bechira to kill a large percentage of kllal yisroel is kefira needs solid mekoros for it to have any weight.
Do you believe that the Nazis did NOT have bechira? Do you believe with 100% certainty that had they done nothing everyone would have been killed and experienced that suffering some other way?
The Torah very clearly says that Klal Yisroel would be enslaved but the well known Ramban (Breishis 15:14 says they had the bechira to be more benign and that the MURDER of Jews committed by the Egyptians (like throwing the boys into the Nile) was something they had complete bechira over .. Among many other sources that would support the concept of goyim having bechira to decide the fate of a large part of klal yisroel like the case of the holocaust. There are Rishonim who give other reasons for why the Egyptians were punished but no one who argues on the Ramban and those who say like him so strongly.
What is your source for saying that believing that goyim have bechira to determine the fate of a large part of klall yisroel like the holocaust is kefira?