Billionaire Masayoshi Son may be getting closer to achieving his dream of making SoftBank Group Corp. the world's biggest investor in technologies, thanks in part to the main patron of Son's $100 billion (¥11.3 trillion) investment plan — Saudi Arabia's Crown Prince Mohammed bin Salman.

The Saudi prince has been the largest investor in the SoftBank Vision Fund, contributing almost half of the money Son has been raising to accelerate his dealmaking around the world. And since November, Salman has been at the center of an unprecedented purge of officials and political rivals in the oil-rich nation, leading to a consolidation of his power.

A stronger Salman could mean steady flows of Saudi money into the fund, which allows SoftBank to make investments without adding to its heavy debt load and offering the potential for those investments to generate revenues to pay down the burden. At the same time, any unforeseen reversal in the prince's fortunes may raise questions about the sustainability of his investments.