I don’t think this is just Johnson, it seems that any speaker is taking this course, why? Investigation and impeachment appear to be an appropriate path for what most of us are reading and hearing on the matter. What are they hiding or protecting?
It would be a bit out of character for Republicans do the smart thing - but maybe they are this time: Impeached Presidents have historically done very well in their re-elections - one could argue being impeached would help Biden.
Also, impeaching Biden now would almost certainly cause the DNC to dump Joe and run Newsom instead. Do we want that? I’d rather Trump run against Biden.