Makes sense to me in a lot of ways.
And the market's reaction, well, it's just objectively stupid, based on simple math. If SCTY is valued at 2.1b right now, and TSLA is buying it for 2.5b, sinking TSLA's mkt cap by 3.5b (which is where we currently are) suggests that the market actually thinks SCTY is worth -1b to TSLA. That doesn't make any sense. I could see TSLA's mkt cap going down by 400m based on the premium which is being paid for SCTY, but 3.5b? Nobody's doing the math on this one.
As a long time shareholder, this is probably the first move I really disagree with Elon. Tesla as a company to invest in had a simple and clean book, and easy to understand business and valuation. No offense to fans of Solarcity, but to me it has business model that is make-or-break depending on government policy and a very complicated book of long term leases and ownership of panels.
I really don't see any deep synergies beyond what could be accomplished in a tight partnership, except maybe unified branding. Maybe it's the right move longer term and Elon is picking up a deeply discounted business, but this will at best be a minor distraction for management in the coming months. Right now we're at a critical make or break phase for Tesla with the Model 3 launch, and I wish they would simply focus executing that to perfection.