I think that the following study goes a long way to explain that.
"New Study by MyHeritage Reveals that Hungary Has the World’s Second Largest Percentage of Population with Jewish Ancestry"
https://blog.myheritage.com/2019/08/hun ... yheritage/
Hungary’s lead grows further at lower thresholds for Ashkenazi Jewish ethnicity. 12.5% of the people tested in Hungary have 10% or more Ashkenazi Jewish ethnicity, compared to only 4.7% of people in the USA and 4.0% in Canada. Meanwhile, 4.2% of people tested in Hungary have 50% or more Ashkenazi Jewish ethnicity (equivalent to having at least one parent who is fully Jewish), compared to 2.3% in the USA.
This is significantly higher than some recent estimates. Official statistics set the number of Jews in Hungary at only 10,965, according to the 2013 national census. Alternative estimates, such as the estimate produced by Professor Sergio DellaPergola, show that the number of people in Hungary who self-identify as Jews — for example, when asked in a survey — comes to 47,500 people or 0.49% of the population.
The figures shown in the study are consistent with the expected number when it comes to the other countries, its only to Russia and Hungary that the numbers are incredibly higher than the ones previous believed.
So, where did all the jews went? They went exactly where Hitler said he was gonna put them, to the East/Soviet territory