This investment was possibly made earlier than when its announced. This investment must have been in January when bitcoin was still ranging around $30k and its really been on the rise even before the announcement.This is a huge investment made by Elon Musk. He made this move in order to reward the shareholders in his companies.
I can remember three days ago Mr Sowyer convinced in to invest in Bitcoin you know that will increase the share value of his company.
And the news carried out yesterday that he had made the investment. I think this is one of the major factors why bitcoin is hit new landmark $46000.
If the price of the Bitcoin falls it will definitely has effect on the price of the company's shares. However, this kind of investment is not for a quick profit but a long-term investment.