MSP had no intention of paying back R&M, certainly not in the short to medium term anyway.
They were essentially going to purchase the club over an extended period, increasing their shareholding in something like 25% increments. They basically raised the money for their initial 25% from their investor pool and would look to raise further cash to cover future increments at relatively fixed points in the future.
The issue was that R&M have the right to request their loan is repaid partially or in full upon any change of ownership and in this case they viewed MSP's investment as down valuing the club. By all accounts they wanted partial repayment of their loan but MSP didn't have the money to do so and Moshiri wouldn't use any of his own capital. Hence it then turned into a straight loan from MSP to cover the stadium build.
Somthing along those lines anyway,
MSP don't have the capital to purchase the club as a whole, not unless Moshiri was giving away his equity, writing off his loans and they had the ability to re-structure our remaining debt over the long term at a much lower interest rate.