The biggest part of a "good interview" is getting the guest to say "yes" to being interviewed.
The issue that people overlook with "challenging questions" is that the guest must agree to be interviewed in the first place. If the interview is denied, then the "lack of challenging questions" is a moot point because the guest never made himself/herself available to be made uncomfortable.
In other words, let's say Lex starts out of the gate 3 years ago with a hard-hitting style. This instantly increases his rejection rate and decreases his guest count. Then later guests he tries to pitch to also look at those previous challenging interviews which is distasteful to them and they also decline the invitations creating a snowball effect.
You can't replay history with (as of today) 160 podcasts and say they should have been more challenging -- because we wouldn't even have the 160 podcasts to complain about.
Yes, journalists like Kara Swisher like to challenge/ambush/provoke/etc their guests but not everybody wants to be interviewed by her. See the chicken & egg issue?
Lex isn't poor at challenging questions. In reality, he's building a body of work that solidifies his reputation for interviews in a friendly conversational style that doesn't threaten the guest. This reputation attracts many types of guests that a bigger journalist like Kara Swisher can't get.
