why is it obama can only win a caucus and not a primary? In a caucus people just group together and get counts

Because , elder people can not hang around hours upon hours without seats to place their vote in a caucus . Hillary's people have lives and other things to do. Like jobs, families to take care of, or places to go to. a life.

IMO the primary vote should be the only vote.

He has won more contests than Hillary. He has won the majority of the popular vote, and is ahead in delegates. Your question makes no sense. You are talking only of Texas, what about all the other states Obama has won? Do they suddenly not count.

Not sure on the primaries, but it could be explained that he wins caucuses (or is it cauci?) because they are done in public. As has already been seen, anyone publically not in favor of the Obama-man is oftentime perceived as being prejudiced or worse.

He's won a zillion primaries....are you even paying attention??

Probably because his supporters are more loyal and more invested in his success and he has won plenty of primaries by the way.