If they raised it as equity, they would have to give away a percentage of the company - which gives a 'valuation' to it. So, if they raised $1B for 10% equity,

If they raised it as equity, they would have to give away a percentage of the company - which gives a 'valuation' to it. So, if they raised $1B for 10% equity, the valuation of the company's worth would be $10B. To avoid this hassle entirely, they raised it as 'debt'. The reason being, if they had to give away more than 8.5% of the company for the $1B, the company's valuation would have gone 'down' which can give off a bad vibe/look.