The reasons for this were given by film producer André Szőts in lectures given at the Eötvös Loránd University and in a 2004 television interview on Hungarian television TV2.
According to Szőts, Hungary provides for a relatively cheap budget (e.g. salaries are much lower than just about anywhere in the West), and Budapest has kept the image of a city that is so diverse in building types from different eras that it could be substituted for (or disguised to be) any large European city.
Szőts has given an example of a French film he produced in which Budapest was a set for 30 different cities.
Un eroe Italiano aka A Kind of America Jason Statham US: USA Network original, Internationally: Amazon Prime Video original series starring Will Smith starring Ryan Reynolds 2020, Dec 23 Budapest is the sole filming location for the entire film Premiered on covid-era formerly-known-as HBO MAX and in cinemas.
airs March 24, 2022 – May 19, 2022 Marvel Studios started filming March 2021 in Budapest RTL+ Hungary, 10-episode mini-series December 20, 2024 (United States) The following films or television series episodes had a plot or part of a plot set in Budapest but were not shot on location.