How is Blockstream going to recoup its 71M VC with sidechains?
There are a lot of ways they could make money off of sidechains. As one of the only companies with developers who are experienced with making sidechains, they could provide a service where they make sidechains for people. They can also make permissioned sidechains and require people who want to use said sidechain to pay them some fee.
There is currently no market for 'making sidechains for people'
However there is a market for transacting in Bitcoin.
Very rarely does VC pioneer new markets as opposed to funding an operation with a solid
business plan to serve a hungry, existing market.