I don't have any background in finance, but it seems like there are a couple of possibilities.
First, given the recent precipitous fall in the NASDAQ, there's speculation that Musk will lower the offer (which seems quite reasonable).
Second, I'm not sure there's any reason to assume these new equity investors are paying the share price Musk is paying. If Musk pays $54.20 a share, and needs to raise 25% of the acquisition cost by issuing new equity, he could sell 49.99% of the new company at say, $30 a share to his partners and still raise the required capital.
First, given the recent precipitous fall in the NASDAQ, there's speculation that Musk will lower the offer (which seems quite reasonable).
Second, I'm not sure there's any reason to assume these new equity investors are paying the share price Musk is paying. If Musk pays $54.20 a share, and needs to raise 25% of the acquisition cost by issuing new equity, he could sell 49.99% of the new company at say, $30 a share to his partners and still raise the required capital.