A SPAC is a company that goes public with no actual business venture, but the plan to buy other businesses. For a company to go public requires a lot of work and disclosures. For example, how many subscribers, how much revenue, etc, etc. Truth Social is a dud. This would have to be disclosed clearly. However, if a public company buys a private company, the public company does whatever due diligence it chooses. Thus, the SPAC was created to be a public company that would buy Truth Social, since the SPAC has no actual business, it can get through all the due diligence quickly and easily. Thus, Truth Social could, essentially, become a publicly traded company without going through a time-consuming IPO (which would require it to disclose things like subscribers, revenue and profits).
However, it’s illegal for a SPAC to have a plan to buy a specific company in advance, ie, for a SPAC to be used as a way around the due diligence and disclosure requirements of going public. This is a particular problem for Truth Social because it’s almost certainly worth nowhere near the price $875M that was, I believe, raised for the deal.
If the SPAC operated legally, it should be able to buy Truth Social for far less than the original deal, allowing the SPAC to buy other, more promising companies with the remainder of the money they raised.