Nobody shut Parler down. Parler's vendors made business decisions to stop taking their money and stop providing services. There is no law against Parler, and no government action. Conservative voices are still all over Twitter and Facebook (see example below). The alternative is forcing AWS to host this content which has some pretty nasty implications too.
8/10 top posts on Facebook in the last 24 hours are from Trump-aligned sources:
Ben Shapiro is Trump aligned? Why because he voted for him?