Sometimes defend titles with a mandatory is more difficult than fight the best.

I want to know if that makes sense.
Last night Joshua made me think about this.
Is it possible that sometimes to defend a title with a B or C level fighter is more difficult than conquer a title with a A level fighter?
There are many example of great fighters that shine on the very best night and struggle when they have to fight their mandatory, or when they have to fight some unknown fighter because of the lack of good fight to make (Ennis the match before the last one, Prograis last match, Taylor vs Catterall, just to say a few).
If thats not the case, we dont explain ourselfes why in the modern era, or at least in the last 5-10 years, world champions defend much less their own title compare to old fighters (in the same amount of time, Trinidad 15 defences, Spence and Crawford for each).
We often forgot that lower level fighters is always very hungry and prepare himself like it would be no tomorrow, and you are a champion yet - and more talended. Its easier when you have the right motivation because you have fo fight the best of the best, but when you are a wondeeful boxer, how you react to 3 or 4 fight against fighter who are not on your level? Often champions perform under the expectation.
I also think that that the most upset in boxing is related to this thing. Its not like that the champions become trash in one day, but its because of the motivation. Overall Taylor remain a very good fighter even if he lose to Catterall, for example, or Lewis if he lose to Mccall or Rashim. Why people dont keep in mind this, and tend to diminsh the fighter who they dont like? Also, if i say, for example, that Ryan Garcia is trash, and im a fan of Davis, in the same time why i would have to celebrate davis for winning a fight with a tomato can?
You hear this every time two great fighter fights each other: as soon as one defeat the second (spence crawford, lopez loma, usyk joshua..), one became the greatest and the second the most overrhyped in the world (and they dont own up their contraddictions).