No he clearly fell in love with her as a person hence he went through the hassle of getting her into Belgium. I do not see anywhere that it's implied he just wanted a sex slave, you've perhaps embellished too much from the story.
Anyone with a bride-mail-order mentality looking for a trophy wife would do that.
His status, their age difference, and their difference of backgrounds all suggest to me that that was the case.
And finally, the very fact that he did do this, instead of looking for an equal partner locally, is another reason. It was a pure deal - sex in exchange for a better standard of living of his wife. (What did he have to give to a Belgian woman that she didn't have already - nothing, that's why he resorted to an "easy sex scenario".)
Had he genuinely loved, cared for, and known his partner, he would have spotted "her" infidelity and true identity long ago. Possibly, if he did love "her", "she" wouldn't need a reason to cheat or it would be extremely difficult for "her" to pull it off as he would have had her attention all the time. So, I conclude, he only cared for himself and should have known better. Yes, he was naive and he was used by a scammer, but that's just life. He put himself into such a situation and is fully responsible for 19 years he has wasted. I have no pity for him.