How can I prove a “genuine and realistic commitment” to continue my business and investment activity in Australia after the complying SIV matures?

Yes, you need to show to Australian Immigration how you make business/investment contribution to the Australian economy once the AUD5Mill matures. This is to avoid that people park the AUD5Mill for the purpose of getting permanent residency.

This criterion for grant of the permanent 888 visa is satisfied by the applicant including a signed declaration as part of their visa application, and providing broad details of their long-term business or investment intentions. A definitive long-term business or investment plan is not required, but applicants should demonstrate an understanding of the Australian business and investment environment in which they would be operating.

My advice is to write a statement (i.e. a story) about why you want to stay in Australia after the SIV matures. In other words, if you can invest $5 million, you would have had life experiences that made this money and also decisions as to why you would want to stay. For example, this statement should include the following: (1) background information about your personal life and business history (successes and failures), (2) your current relationship with your partner and kids, (3) any extended family / relatives living in Australia, (4) any friends who already live in Australia, (5) the Australian environment compared to the places you have lived, (6) future business prospects in Australia (other than your SIV investments), (7) future education prospects for children (if you have or plan to have children) (8) intended home/residential purchases in Australia (9) intended business acquisitions in Australia, (10) future relationship plans with your partner, (11) any other work/life balance/strategies/decisions.