This was, in large part, because people were given near total freedom (far more of it than you see in the US today) in one fell swoop, and _way_ before they knew what to do with it. Naturally, some people were much better than others at turning this to their advantage, opportunistically injecting themselves into the corridors of power, buying up previously state-owned factories for fractions of a penny on the dollar, swindling the common people out of whatever breadcrumbs the government threw to them during privatization.
This shit was allowed to run unabated for a decade or so, and ended up with Yeltsin hanging up his hat and apologizing on TV, before de-facto installing Putin as his successor. The people behind this were Siloviki: the powerful folks who run or otherwise control Russia's several security services.
In retrospect, given the amount of pain, death, and suffering inflicted on the general public, it could be that shooting a few hotheads early on would be an objectively better option. The country could then proceed to a much more controlled and measured liberalization, with law and order carefully enforced throughout, rather than a decade-long free-for-all (or rather "a few") that ensued in practice.
That's not to say that Tiananmen suppression was justified. I grew up in Russia, so I was a direct observer and participant of the events I describe above, so in the case of Russia I can tell you with a good degree of confidence that if the wild 90's weren't allowed to happen there to the extent that they did, Russia would be far better off.
Stuff like this also can't be judged by reading propaganda, foreign or domestic, so those who haven't been there at that time should refrain from commenting one way or the other. That'd be just regurgitating someone else's talking points: an entirely pointless exercise.
I'd love to hear from someone who lived in China at that time and for whom this is not something they've read about on the Internet.