Satan Exulting Over Eve

What exactly is happening here? We have Satan above, Eve below, with the snake wrapped around her. This William Blake painting is from 1795, in the Getty Museum, Los Angeles. The Getty website says that "Satan hovers in malevolent glory over Eve" but this pose hardly seems malevolent. Meanwhile the Tate (London) says "Blake’s Satan bears none of the marks of depravity or bestiality that one might expect." Why would we expect that? Neither appears to understand Milton's Paradise Lost; Blake clearly does.