Socialism

Life expectancy rose before the end because that's when the USSR focused on curbing the rampant alcoholism, which causes cardiovascular diseases (the notable weakpoint in the USSRs healthcare system and a major reason why life expectancy failed to rise further under the USSR). This wasn't a temporary stall, that wouldn't last that long, there's systemic reasons for it. The USSR lagged behind quite significantly compared to its capitalist peers.

The skyrocketing problems the USSR experienced post-dissolution are obviously triggered by the switch, but it becomes hard to argue that capitalism as a system caused it, since capitalist peers don't actively suffer the same issues, and Russia since its recovery doesn't either (as it is still very much a capitalist world power). It's clear the switch was bad (horridly mismanaged), but the final result is that life expectancy rose above what the USSR ever achieved, finally reaching an on-par status with its peers.

To be clear, I'm not arguing that socialism couldn't achieve this, or that capitalism is the better system or anything. But I am challenging the assumption that capitalism is the cause of a lowered life expectancy, since the graph you presented didn't exactly support that statement (given that under capitalism Russia's life expectancy rose well above what the USSR ever managed).