It has kind of become like a norm that most men either hate to get into commitments or take a long time in doing so. So, it does come as a surprise to women when their man is overly eager to get committed. Below might be some reasons for that.
Reasons from the past
Maybe he has been in a relationship where he loved his woman and was absolutely committed to her and spent plenty of time and effort only to be dumped by her. So maybe his past insecurities are making him rush if he feels that you are the right one for him.
He is head over heels in love with you
Everyone has heard of the love at first sight syndrome. It is possible that something like this has happened to him regarding you. He has eyes only for you and you have become his centre of universe. So, obviously he sees no reason for any delay of any sort.
He may have territorial instincts
Now every woman has their set of admirers. If he is in some way interested in you, then his natural instincts would tell him to put a fence around you in an effort to keep the other guys at bay while he take his time to sort out his own feelings about you. In his mind he just wants the security that you do not fall for someone else in case he wants you for himself.
He is completely sure of his feelings
It is human nature for the mind and heart to be in conflict most times. But it can be that he in his whole being is very sure that you are the one and only for him. He will then find no reason for waiting.
His mind has made him insecure about you
Now he might very much be in love with you and if at all he has seen something in your behaviour or mannerisms that tell him that you might be losing interest in him, he will just push the panic button and offer his commitment sooner than you think due to fear of losing you.
Maybe he has been there forever on the scene
It might be possible that he has gone around and dated a lot of women in the past only to have been disappointed by every one of them in some way or the other. And so if he likes you, he feels the need to be quick for commitment before his mind undergoes a change too.
That need to feel settled
Bachelor days are not going to be around forever. Every man at some point of time in life wants to settle down. And if he feels that you are that special one for him, surely he is not going to hang around for long.