Your "friends" appear to have committed fraud and breach of partnership. By inducing you to establish a business on the premise that you would have a long-term lease, and then stalling the final agreement while waiting to see if you were going to be successful, they made a false representation
of fact, intended to induce detrimental and justifiable reliance and causing damage, and that is the classic definition of a fraud.
Assuming the fraud, you have damages against them on that legal theory -- however, because there was no true agreement to lease, your friends and you may have entered into a general partnership, which is an association of two or more persons to carry on a business for profit. Your friends contributed their lease and you contributed your business model and operating skills. So, you could also sue for an accounting and dissociation of partnership, and your friends would either have to buy you out, which could mean ongoing payments for your interest, or reinstate the partnership with you as an equal partner.
I'm noting this partnership theory, because if you sue for fraud, your friends may counter that there is a partnership, because the alternative is that you end up with a large damage award, and your friends with nothing. Whereas if they were to establish the partnership, then you would all be business partners and all entitled to a piece of the action.
You're going to need a business law litigation
attorney. This is not "Judge Judy." If you want your business back, you will have to fight, and that will cost money -- both for you and for your friends. Considering just how much the litigation could cost, you may be able to reach a quick settlement to keep everyone out of court. But, without a lawyer writing a threatening letter, your friends won't believe you're serious, and they will simply ignore you.
For a competent attorney referral, see this link