Jiri and Hill did not defend their titles against anyone other than Alex. How can they lose their belts? Jan did not beat everyone, he only defended his belt once, and it was against Israel Adesanya who did not bulk up to 205.
I'm not discrediting Alex for fighting who is available, but you're making it seem like no one has ever won against 3 guys as good as Hill, Jiri, and Jan since Jon Jones was champ, which isn't true. That's not to mention that the best 205ers were in the UFC during Jones era, which isn't true of the last few years in the UFC.
It's not comparable to Jon Jones destroying Shogun, Rampage, Evans etc.
Someone like Hill was never a top 5 LHW of the world if you analyzed what other LHWs were active at the time. So what is the utility of stating he is a former champ? It's trying to make him look better than what he is.
Peireira hasn't beaten more champions than Silva regardless, and the standard is silly because divisions like MW had less champions because Silva denied many guys from the belt. Once Silva was dethroned the belt was carried by many different guys until Adesanya.