He hasn’t beaten impeachment twice. He has beaten it once. The second impeachment is ongoing and as of now, no vote has been held. Congress are currently debating it.
In terms of what it will do, it will have a massive effect. If impeached, he is banned from running for public office again so prevents him going again in 2024. Allows the Republicans to move on from Trump.
But a more wider effect of impeachment if successful is that it shows a president cant get away with inciting insurrection.