It's not about "afford" (insurance is, after all, a profit-generating business), it's about being able to.

They have the resources to make their own insurance company.

The question is, will this company be recognized by all required players (ports, authorities etc.). If you're insuring something worth hundreds of millions of dollars, you really want the insurance company to meet certain standards, and have a good reputation of paying out. Can Russian achieve that? Probably. Can they do it quickly? That sounds much trickier.

If Russia doesn't back its insurance it loses credibility around the world.

Russia is a major player in the oil world. It has the relationships and experience to manage this.

Russia is massively underdeveloped. It would take a few trillion dollars in funding just to extract a relatively small fraction of those known resources. They are also massively under populated. They do not have the financial nor the human capital to even extract a 1/10th of that wealth in their current state.

China had invested a lot in Russia in the Belt and Roads initiative to extract natural resources, and it is looking like Russia will default on those loans.