I think they are just excited with the mere thought of a big company putting in their trust and money into bitcoin the way they do that it justifies or validates their own decision to invest as well. This also increases positive general opinion towards bitcoin. I know we shouldn’t have to follow big companies or any other individuals but maybe they still look for some validation from “experts”.
All this anticipation and excitement from major institutional investors drive up the price of Bitcoin. It's just a usual investment method when it comes to cryptocurrency. People want to see how others find a particular project interesting so they as well make their own decisions to invest..
While Bitcoin's price is influenced by many factors, these fundamentals are key drivers. In the past, institutional investments in Bitcoin were rare, but even without them, Bitcoin's price was still highly volatile. with the entry of these large scale investors, Bitcoin is gaining more exposure and is experiencing a more rapid adoption than ever before.