When Chinese billionaire Jack Ma took a trip to Spain's Mallorca island last month, much was made of it being his first foreign foray since a 2020 fallout with regulators had clipped his wings.However, Ma's sunny sojourn on his newly-built 88-metre (289 ft) cruise boat Zen - estimated to be worth $200 million - also put a spotlight on a global trend: the return of the superyacht.As the number of billionaires grows and COVID-19 has added to incentives for avoiding crowds, the multi…