How did he get away with all the consecutive fifths and octaves that he uses? Any other Baroque composer avoids them like the plague, but he throws them in like nothing. Was he a bridge composer to the classical era?
Scarlatti is a most obscure historical figure. It is as if he was doing everything in his power to remain anonymous. There is no correspondence, no mentin of him on courtly affaird, almost no documents.
In 1770 (Scarlatti died in 1757), Burney visited Farinelli – the castrato who was music director at the Spanish Court at the time Scarlatti was there – who had retired and now lived in Bologna. Their conversation – and the book Burney subsequently wrote – are the most detailed information we have about Scarlatti.
This bit of Burney´s account (“The Present State of Music in Germany” vol 1) may be of interest.
“Scarlatti frequently told M. L´Augier that he was sensible that he had broken through all the rules of composition in his lessons [sonatas]; but asked if his deviations from these rules offended the ear? And, upon being answered in the negative, he said, that he thought there was scarce other rule, worth the attention of a man of genius, than that of not displeasing the only sense of which music is the object.”
So, basically he got away with it because it sounded good!

(A very similar posture was adopted by Debussy when criticized for not following the rules).
Best wishes,
Bernhard.