As the open access movement has gained widespread popularity in the scientific community, academic publishers have gradually adapted to the new environment. The pioneer open access journals have turned themselves into megajournals, and the subscription-based publishers have established open access branches and have turned subscription-based journals into hybrid ones. Maybe the most dramatic outcome of the open access boom is the market entry of such fast-growing open access publishers as Frontiers and Multidisciplinary Digital Publishing Institute (MDPI). By 2021, in terms of the number of papers published, MDPI has become one of the largest academic publishers worldwide. However, the publisher's market shares across countries and regions show an uneven pattern. Whereas in such scientific powers as the United States and China, MDPI has remained a relatively small-scale player, it has gained a high market share in Europe, particularly in the Central and Eastern European (CEE) countries. In 2021, 28 percent of the SCI/SSCI papers authored/co-authored by researchers from CEE countries were published in MDPI journals, a share that was as high as the combined share of papers published by Elsevier and Springer Nature, the two largest academic publishers in the world. This paper seeks to find an explanation for the extensively growing share of MDPI in the publication outputs of CEE countries by choosing Hungary as a case study. To do this, by employing data analysis, some unique features of MDPI will be revealed. Then, we will present the results of a questionnaire survey conducted among Hungary-based researchers regarding MDPI and the factors that motivated them to publish in MDPI journals. Our results show that researchers generally consider MDPI journals' sufficiently prestigious, emphasizing the importance of the inclusion of MDPI journals in Scopus and Web of Science databases and their high ranks and impacts. However, most researchers posit that the quick turnaround time that MDPI journals offer is the top driver of publishing in such journals.
