Solarcity didn't need the bond market.
It did need the financial borrowing market; it is a finicky question as to whether it needed the *bond* market, but in essence, yes, it did.
Solarcity could not profitably play the middle man on the placement of debt secured by solar installs.
Yes, it could, and it did for years. The key word here is "profitably". This is a very different thing from "cash flow positively".
This is shown in Solarcity continually shrinking their ongoing business, even with the ITC still being in effect. Solarcity would not shrink if their activities were they cash flow positive.
They were cash flow negative, and by reasonable accrual accounting (such as will be mandated next year, IIRC) profitable. What is so hard to understand about that?
They were leasing solar panels with 30-year or 40-year income streams. The value of the income stream, discounted to the present day at typical interest rates, is substantially higher than their cost to install. I.e. profit.
However, they don't get this money until years in the future. So they have to borrow to get it -- initially at lower interest rates than the implied interest rates in the lease, but not much lower. That's where the profit margin was. *Pressure on their credit rating was enough to reduce and eliminate the profit margin*.
In addition to borrowing, they frequently sold off the *front half* of the income stream for roughly what it was worth, maybe a bit more. Which is fine, but it means the profit is entirely dependent on money coming in 15 years in the future.
Before selling off those front halfs, they used temporary construction financing with even shorter terms -- like a year. So they're borrowing on a one-year basis to finance a 30-year income stream.
This is the business model of a bank, which takes your deposit (withdrawable at will) or your purchase of a 1-year CD, and uses it to finance a 30-year mortgage. *It is badly subject to bank runs and cash flow issues*. It is also subject to rising interest rates. If you issue CDs at 1% and mortgages at 4%, you're fine. If you start having a bank run and people will only put money in your CDs at 5%, you have a problem the next time you refinance.
This is why Tesla is getting out of the mismatched-maturity finance game (i.e. banking).