No, it's actually because the government alongside some corporations like Mitsubishi had already invested billions in the Sakhalin-2 project. When the invasion started, instead of stopping investments or withdrawing from the project, they've instead chosen to double down by investing more.

Oil price in Japan is fine, there are also a lot of affordable public transports such as bus, trains & high-speed trains (which often corporations cover the cost too).

All of the foreign parties that have invested in the project can totally afford that loss as not only they are massive (Mitsubishi is just that big), they were already aware years before about the potential risk of a sudden loss of their shares so they are prepared for it.

So no, that decision is just a lack of morals & greed. Now that they have affirmed their commitment back in August 2022, they'll have to cooperate, provide technical support, spare parts, etc. which means untouchable by sanctions guaranteeing a tremendous profit for russia (60% of share) on the long term.