I think, also, that Lex's voyeurism of Lana just goes to reaffirm that her role in his life replaces Clark's. Although I don't believe Lex will ever not have some modicum of interest in Clark['s secrets] (and his extreme attention to Lana will never match his obsession with Clark), he is redirecting this attention to Lana now.

This is the same as how TPTB always equated Clark's friendship with Lex as equal in power to his feelings for Lana.