Legoland was created by builders.
Builders, an group that was recognized by Lego as extremely talented creators using lego bricks, were oftenly recruited by Lego after they had been recognized in competitions.
These champions for the competitions were then gathered to design, and build various large lego projects, including the ones you seen in legoland, and many of the lego shops.
Many of these projects include large lego figurines, sketches of human in lego bricks, buildings, large robot figurines, animal figurines etc using not less than 1000 lego bricks to construct.
Builders are being paid handsomely for their construction and some projects may require more than 5 builders to construct due to its enormous size. Special plastic glue and bricks were all provided by Lego during the construction.