Maria Callas: Investigating changing her voice

I investigated the voice and larynx of Maria Callas. She was an American opera singer, famous for her impressive vocal range.
People say that her voice has noticeably changed since the 1960’s.
I often hear that this problem was caused by stress due to an affair scandal as well as aging.
I’ll investigate what the underlying reason is, in why her voice changed.
I’ve found the position of the larynx and the status of her neck muscles in her photos.
Her larynx looked so flexible when her voice was in its heyday before 1960.

You can observe the laryngeal prominence in the following picture:


Meanwhile, the muscles of her larynx appear to have tension, when she had a slump in singing after 1960, and the larynx is positioned deep in the following picture.


Through visual observation I conclude she contracted and strained her throat when singing. I speculate that could be from not using her voice for an extended period of time and then returning with expectations of having the same abilities. Control, flexibility, and strength will weaken if the vocal muscles are not consistently being exercised. It is especially important for opera singers to maintain the muscles of the throat in order to keep the ability to project such powerful vocal volumes and push to such wide vocal ranges.
Although I do not know the specific incident that caused the issue to her throat, sequentially she could not control her voice easily with that problem.
She had a long distance between top of the hyoid bone and the mental spine of the mandible, it is muscularly defined and this portion resonates the voice greatly.
Her voice attracted many listeners.