Who Paid the Pipers of Western Marxism goes in-depth into this.

There's an entire industry of ideological production to create non-revolutionary "Marxists" that reject the contributions of non-Western Marxist theorists and revolutionaries. Their job, which has been largely successful, is to recuperate Marxism into a form that is class collaborationist, aligned with Western hegemony, and (most importantly!) aligned against actually existing socialism.

They're not just online here in the West. They're respected in academia, they're on TV, and they're always publishing works.

Some are baby leftists grappling with decades of propaganda.

Some are opportunists trying to alter the definition of words and dictate discourse so they can hijack popular socialist rhetoric for anti-socialist goals.

Some are genuinely confused and haven't fully grasped the contradictions of liberalism; believing the liberalism they see all around them is in fact a distortion or corruption of liberalism rather than actual liberalism and so are ideologically liberal while espousing apparent anti-liberalism because they don't understand that the consequences of their ideals when put into practice results in the very system they claim to oppose.

I think this just happens when they see problems with the current system (a natural consequence of living in capitalist society) but still dogmatically support it. Anarchism and "non-communist leftism" and "progressive" liberalism are useful to the capitalist state because they allow people to question and oppose what's happening in our society but still come to the conclusion that almost nothing can be done. It's not a big leap for people to say that imperialism is bad or that people's basic needs should be met, but it takes a lot for masses of people to turn against ruling class ideology, so it's expected that these kinds of leftist/liberal identities would be common in a capitalist society.

I think most think they are either further left than they actually are or just don’t understand the label.

I mean, Liberals adopt Leftist personas all the time, e.g. Karl Kautsky, Bill Clinton, Ian Kochinski. As for the purpose, it mostly seems to be:

• to fill the Left with tons of reactionary opinions like the need for border security;
• mislead the Left by misrepresenting actual Leftist arguments such as "decolonization" and "Socialism in one country";
• and making the Left feel hopeless by demonizing actually successful revolutions such as the USSR, PRC, Cuba and DPRK.

I suppose the consequences of Liberalism would be such balderdash being found out. Liberals are otherwise quite respected across the First World, and don't really need to hide themselves in shame.