Complex sentence: Although the Third Way movement was at its peak in the 1990s and 2000s, it has since been on the decline and by 2017 it become clear that the ideology is not as popular as it used to be outside of established Third Way circles.
Split into simpler sentences: Although the Third Way movement was at its peak in the 1990s and 2000s, it has since been on the decline. By 2017 it become clear that the ideology is not as popular as it used to be outside of established Third Way circles.