Got a Swagger of a Champion
Womanizer's charm is effective for one main reason – he can offer a woman anything she wants to find in a man (the reason why the whole thing ends up tragically is because she gets it in a not too genuine manner and only for a short period of time...). One of the most wanted-by-women qualities in a man is confidence. Any Casanova can boast perfect confidence in himself and his powers, and that charms any woman.
A womanizer is typically a man who is one hundred per cent self-confident. He has met women of all the types and characters, all appearance-levels and all statuses; he is well educated regarding the power of seducing any kind of woman, that's why his confidence is rock steady under any possible circumstances or conditions.
Casanova's confidence shows in every possible behaviour-point he reveals – in his divinely perfect clothes (loves spoiling himself, or being spoiled rotten), in his movements (loves showing his irresistible charm and knows it works better than words sometimes), in his words (words still do matter for a woman loves with her ears very often), his walk and the way he talks with people – both men and women.
Don Juan knows he is handsome, he knows he is charming and magnetic, he is perfectly well aware of all his wicked virtues and he makes the most of this awareness by making any woman fall at his feet and wanna do anything he says.