When did "visionary" become a good thing?

As  faithful readers of this blog (are there any?) may have noticed from the non-fiction book reviews, I've been reading a lot on the 19th and early 20th centuries.  One thing I've noticed is that in that period, the use of the word "visionary" seems to have been uncomplimentary, following Merriam-Webster's definition 1b: "incapable of being realized or achieved."  When people of the 19th and early 20th centuries referred to a "visionary scheme" they meant it was impractical.  For example, the Samoa condominium established by the 1889 Treaty of Berlin was referred to by some German leaders in a derogatory manner as "visionary."  A decade later it failed and was replaced by the Tripartite Convention of 1899 that partitioned Samoa.  I've encounter no instances I can recall from that period where "visionary" had a positive connotation.

However, in modern usage, it is usually a complimentary term, following Merriam-Webster's definition 4: "having or marked by foresight and imagination." I cannot recall a single usage of it in the negative sense in modern use.

So questions now run through my head.  When did this change?  Why did it change?  These are not the world's most pressing questions, I will be the first to admit, but they do make me wonder.