SPACs.....exist solely to raise capital through an IPO...
That's a little simplistic, the clue's in the name "Single Purpose Aquisition Company". The problem they exist to circumvent is that the rules around an IPO are quite stringent when it comes to the viability of the company being floated. Thus what you do is float a company that does nothing, the SPAC. This has books that say it has ${cash}, no liabilities and no expenses and thus easily meets the financial criteria. The SPAC then takes over the real company and as there are no pesky viability rules for takeovers, this goes through.
Presto, a dodgy, high risk business successfully floated without its murky books and iffy practices being pried into by inspectors.
The interesting thing here is that taking this approach is almost invariably more expensive than an IPO, as everyone involved takes a cut, but companies still do it. The fact that they're happy to shell out, purely to avoid proving they meet the financial criteria of the stock market, gives you a really good clue as to how sound their business actually is.