Communists won the election in 1946 and formed a coalition government in which they were the strongest force, but not completely dominant. There were other "bourgeoise" ministers. Unfortunately, Communists controlled the ministry of the interior and cleansed the police of "reactionary elements", thus cementing their control over the civilian law enforcement. Not over the army yet, though.
There were regular elections scheduled for May 1948 and opinion polls were indicating that Communist share of vote is actually going to diminish. So they preempted them by staging a coup supported by People's Militias (a completely illegal armed militia of the party) on February 25, 1948. After that, the democracy was toast and it was full speed towards Stalinism, show trials etc.
Some of the army generals wanted to suppress the coup militarily, but the aging President (Beneš) did not allow that. IDK if it would have been better or worse. Civil wars tend to leave a very toxic legacy.