Boguslaw and Janusz Radziwill (leading middle 1600s Lithuanian Protestant leaders) were strong, helpful personalities to Unitarians, Jews, and other group, but are missing from the pages of the History of the Polish Reformation (HPR), a seminal document in Renaissance Unitarian history, except for brief references in the Editor's notes (by George H. Williams) to the fact that other prominent Unitarians worked for these Radziwills of the 1600s.
Why are these Lithuanian progressive leaders — a prime minister and a head of the Lithuanian army — essentially invisible in the HPR, written in 1661-1675, when by contrast we know from Lithuanian, Jewish, and Belarusian-Swedish historians that the Lithuanian Radziwills of the 1600s received and recruited the Polish Unitarian leadership for high positions in government and business in the Grand Duchy of Lithuania following their exile from Rakow, Poland in 1638? These 1600s Radziwill figures were strong upholders of the laws and statutes regarding tolerance, and architects of private programs bringing religiously persecuted families and communities of all denominations and religions from all over Europe to free private land in Lithuania. These Lithuanian Protestant leaders, in policy and instinct, were in civil liberties and social thinking very much like 21st Century Unitarians even though their religion was a progressive Calvinist one.
My short paper linked below offers an explanation — that the most senior of these leaders, Stanislas Lubieniecki, author of the HPR itself, was known to be Boguslaw Radziwill's secret emissary to the King of Sweden to explore a possible Union to replace that with Poland. When the Counter-Reformation took over Lithuania in 1658 after a series of crises and war, the Radziwills were accused of treason, although they were later exonerated.
My conclusion is that, faced with risking problems for himself and the exiled communities because of the taint of treason or other matters of unpopularity, Lubieniecki decided to leave out all references to the Radziwills of the 1600s from his historical account. By contrast, references to the Radziwills of the 1500s are well represented in the HPR.