Thunder trade James Harden

How stupid... I do not understand at all why the Oklahoma City thunder would trade one of there key players. Yes, I under stand they have Kevin Durant and Russell Westbrook but I believe Harden is very under rated. Also, I worry for how the thunders chemistry will be without him because I always saw him as the glue if there team. Now as for the Houston Rockets they get a steal and a possible new face of the franchise and this could be what they need to keep the Rockets in Houston