Here's a sentence from the opening of James VI and I's "A Counterblaste to Tobacco" (1604):
For certainely as such customes, that have their first institution either from a godly, necessary, or honorable ground, and are first brought in, by the meanes of some worthy, vertuous, and great Personage, are ever, and most justly, holden in great and reverent estimation and account, by all wise, vertuous, and temperate spirits: So should it by the contrary, justly bring a great disgrace into that sort of customes, which having their originall from base corruption and barbarity, doe in like sort, make their first entry into a Countrey, by an inconsiderate and childish affectation of Noveltie, as is the true case of the first invention of Tobacco taking, and of the first entry thereof among us.
Why were books written this way? Were people more adept at paying attention back then, or were authors worse at writing?
To add onto this if I may be so bold, why are Bronze Age descriptions/texts/etc. so long and winded as well? The Bible is a good example of constantly adding information to a sentence. Maybe I'm wrong but that's the impression I got once.
Sorry for maybe getting your hopes up, OP.
All Englishmen who came from old money up until the middle, and some until the end of, the 20th century learned Latin in school, and it was the standard against which all literature was measured for a long time. A big part of Latin literary style is writing elegant, slightly convoluted sentences, in order to show that you're a well-educated and erudite individual. Rhetoric was a highly valued skill, after all! In addition, it has a certain regal air to it, mostly because edicts etc are highly formalised texts written to impress the king's majesty upon the reader. This stuck until not so long ago. Certainly many Victorian writers wrote like this, and as far as I know, it continued into the Modernist era, where the individual came into greater focus.
As for your questions, readers would be used to these kinds of sentences. I started writing like that myself in high school because I studied French and Latin, and I kept it up for years. I naturally read a lot of texts with very long sentences (many of the same texts that authors in the 16th/17th/18th century would have studied as well), and so got better at writing them myself. It's a matter of practice, like reading Gothic font, or a foreign language.
Hope this helps, OP!