Why do the people of tamath-hub find it hard to accept their imam/sheikh is wrong?

One reason is that it is because it takes effort to switch. They already made the lazy decision of not bothering with figuring out the truth, and they only take what they are given and be done with it.

So, if you try to tell them they need to put in the effort, they see that as a threat to the comfort they feel entitled to.

How dare I challenge a view they held for so long and make them think or make effort.

You would feel puzzled, why are they so set on that clearly wrong saying?

Well, you are looking at them through the wrong angle.

Consider them again by thinking they are people who are defending their laziness, and boom, their dismissal of your points make sense.

"So, you know more than my imam?"
*puzzled face expression*

إذا علم السبب بطل العجب.

This, again, is just one reason, but it helps figuring out the rest more easily, إن شاء الله.

It's also good to know this is isn't specific to just the blind followers. It's a general concept, and this is just one example where it manifests.

Another example is: ourselves.

—Al-Qaddari