Why some men change so much ?!

I never noticed this guy until he sent me a big bouquet of beautiful flowers at my work place. I even could not guess it's him who sent the flowers( there was no name on th card) as he is only a driver who delivers things to my work place and his job is not well paid to be able to send expensive flowers. He is even not good looking or dress well.Anyway after a few chats with him I decided to give him a chance as he seemed to be nice and have some intellectual potential. We started dating and the beginning was nice. He showered me with expensive gifts(despite his car was old and rubbish, his clothes was old and with holes, he was living with his mother in a room so small and very messy). He met me with his family, he started making plans to live together after the holiday he booked for us. And all that only after a month together. Then he began to change, he become possessive, controlling, argumentative, initially he told me I can ask him any questions and after a month and a half together he said he is taking his words back and I must think carefully what questions I ask.. He told me that I must trust him and not asking him anything. He started verbaly abusing me telling me I am silly , Im ignorant etc. We had a few arguments and he was shouting and screamimg at me. All this was ruining my self confidence. I am professional, leading a team responsible for the health of many people. I get much bigger salary than him, have a big house and a nice car . I did not see the point to tolerate all this behaviour against me so I broke up with him and told him not to bother me anymore.The thing I can't explain to myself is why he started so nice and then turn to rude nasty man. Why he changed so much?