Just to be clear here - the bill has not passed the Legislative Council, however the bill is expected to pass if and when it is listed for a vote due to the pro-Beijing majority. (Lam's announcement on "suspension" rather than "withdrawal" means that debate on the bill will not be resumed indefinitely, however if the government changes its mind again it could list it for a vote in the Legislative Council immediately.)

LegCo's impeachment power was dead letter law from the start - I can't think of a circumstance where the pro-Beijing camp would ever use it, short of perhaps some situation where a previously pro-Beijing chief executive has gone rogue and refuses to resign...

I live in South Korea. In 2016, a lot of members in Park's party voted to impeach the president Park. (In fact, impeachment couldn't have passed without such.) It's pretty simple really. Anyone from competitive seat will do pretty much anything if they are 100% sure they won't be re-elected otherwise.

ROK doesn't quite compare, being a democracy. In fact I was quite surprised to see president Park impeached and saw it as a sign of a functional demicracy. Failing to impeach her would have probably ended in riots.