This statement seems to be factually untrue. Mashayoshi Son owns 32-33% of Softbank and then the investors are like the Japanese Master Trust bank etc. Saudi Arabia is not even in top 10 of the investors list.

Saudi Arabia did recently invest 45 billion dollars in the vision fund which is an investment fund managed by Softbank but they haven't really invested within Softbank itself so not it is not mostly owned by Saudis from what the data can tell.