) So WHY did Bush NOT explain WHY it would take 15 years with 21st tecnology to return to the moon, when it only took 8 years to accomplish this achievement with 1960s tecnology.
Maybe because he assumes that anyone interested in the subject already knew the answer to that question. It's not exactly rocket science, lol.
They are trying to do more than just land on the moon and plant a flag. They are looking to put people there for several months, so they need a bigger ship to transport all those supplies, and time to design and build everything. Nasa doesn't currently even have the kind of rockets that would get us out of the earth's orbit. And of course all this takes money, there is only so much in the budget.
Full explanation here :
http://m.space.com/7015-40-years-moon-landing-hard.html
By the way, it took me exactly two minutes to find this information.
B) Why to my knowledge was this question not raised by journalists at the press conference?
Maybe because they, being good journalists and not lazy, had already researched and knew why.