[zarzavat]

I don't know about Pichai in particular but whenever rich people do things that don't make sense the answer is usually tax avoidance or financial engineering.

If you have many shares concentrated in a particular company that you can't or don't want to sell for legal or tax reasons, you can borrow money to buy a house. As long as you service the interest you get a house without having to sell too many shares and trigger tax obligations.

Home loans are also nice because they are a form of leverage that is secured against an asset but is not subject to margin calls if the value of that asset falls.