Complex sentence: Because they were both relatively important men in a city with only 24,000 inhabitants, it is likely that they were at least acquaintances, as Van Leeuwenhoek acted as the executor of the will when the painter died in 1675.
Split into simpler sentences: Because they were both relatively important men in a city with only 24,000 inhabitants, it is likely that they were at least acquaintances. Also, it is known that Leeuwenhoek acted as the executor of the will when the painter died in 1675.