They are stating that the reason is bad publicity and will apparently turn to Venus Williams.
Another blow for Đoković, although he'll probably find new sponsors soon. Even if not, he already won more than 100 million euros anyway
I believe Djokovic is much more concerned with points and winning grand slams than his sponsors at the moment. As you say, he has more money than he can spend but few more GS titles would go very well with his GOAT candidacy.
Djokovic has so much money that he could also stop playing tennis altogether. He certainly no longer plays tennis for the money, that is no longer a motivation. He is simply in a position not to participate in major tournaments if the corona conditions do not suit him. When Corona is completely gone, it will only get more serious again. Many of his colleagues will also think strangely about Djokovic, tennis players are after all seen as a bit of an exemplary function.