It did survive! And it paints a fascinating picture of adaptation. The Yamnaya cultural package brought elite domination and patrilineal succession. So for the I1 line (mesolithic European HG) to not just survive but spread widely across Scandinavia and crowd out the Yamnaya R1 haplogroup suggests that at least one member of the Hunter Gatherers became dominant over the Yamnaya and beat them at the new Bronze Age game they brought to the region.