>>98984269Lotor is clearly playing Allura. He knew he needed her to get the alchemy knowledge for himself, and now that he has lost that chance he now needs her for actually carrying out his plans too.
That said, I do think not all of his feelings towards her are fake, even if he is using her to further his ends. The way he reacts to the possibility of Haggar being his mother was way too defensive to be part of his act, so he probably really does idolize his Altean heritage to some degree. That, and we have seen him express disgust with the Galra way of life on multiple occasions, even when Team Voltron wasn't around.
So after centuries of reading about Altaens and being weeaboo for them and their magic, actually having a 9/10 cutie patootie Altaen princess in his reach is probably pretty tempting. Its not like there are enough space elves left to form their own civilization anyway, so breeding a stronger magical Altaen bloodline between the two of them has its advantages too.