Over the years, there is one situation that may partially explain why such buildings end up being destroyed due to long-term neglect.
There are some dodgy intermediaries who specialize in selling similar old buildings to overseas buyers, who are the newly affluent class and have less overseas investment experience. The intermediaries packaged these buildings with limited potential into high-value investment assets similar such "majestic Victorian buildings in prime locations". These intermediaries use asymmetric information to persuade such overseas investors to buy these historic buildings, often exaggerating development potential and underestimating risks. Investors may be late to realize that own an old buildings like the Ayr Hotel and reopen for business may requires a large amount of capital investment to rectify the damage and with cumbersome legal paperwork (e.g., do the building's original massive wooden structures comply with modern fire regulations?).
When these investors finally realized that owning and maintaining such an old building was a bottomless pit, they just gave up.
Just do a quick search for "UK real estate investment" in Japanese, and here's what a investment company's website says about investing in old buildings in UK: 建物の寿命は永遠と考えられているので、マンションが古くなることによる値下がりはおきません。むしろ100年以上のものはピリオッドプロパティ(歴史建築)といわれ、値段が上がります。(The lifespan of a building is considered to be eternal, so the price of an apartment will not drop as it gets older. In fact, buildings that are more than 100 years old are called period properties (historical buildings), and their prices will go up.) There is no warnings about the risks of own old building.
Apparently now I have reason to be skeptical of this overseas investment company.