AI, clean energy and defence spending are reinforcing each other, amplifying potential investment, says Rana Faroohar for the Financial Times. NEW YORK: The week of the largest IPO in history may seem like an odd time to wonder if we need more, rather than less, investment into the US and global economies. Many investors believe the SpaceX IPO , with a target valuation of US$1.78 trillion, could signal a top to the technology-driven market bubble of the past several years. Markets will always