The first is the issue of copyright. Generally speaking, if we buy copyright directly from Japan, we will dub it ourselves, but if the copyright price in Taiwan Province Province is lower than that in Japan, we will import it directly from Taiwan Province Province. As the Taiwan Province version has been dubbed, and it is also in Mandarin, there is no need to match it again, saving manpower and material resources.
Besides, it's a matter of time. Generally speaking, due to the historical relationship between Taiwan Province Province and Japan, not only animation products, but also other items including electrical appliances were acquired by Taiwan Province Province before the mainland. In addition, due to the aforementioned factors, most of the Japanese cartoons we see are dubbed by Taiwan Province Province.