I think the goal is unclear, but the effect will be that Codeberg will be perceived as less of a real, stable alternative. Breaking in was not in my mind, but that will have the same effect, maybe even more damaging.
Now, if that has been the intended effect, I hope I won't have to believe that.
Story time:
I remember that back in the day I had a domain name for a pretty hot keyword with a great, organic position in Google rankings. Then someday it got all of a sudden serious boost from black-SEO, with a bazillion links from all kinds of unrelated websites. My domain got penalized and dropped of from the front page.
For threat analysis, you need to know how hard you are to break in, what the incentives are, and who your potential adversaries are.
For each potential adversary, you list the risk strategy; that's threat analysis 101.
E.g. you have a locked door, some valuables, and your opponent is the state-level. Risk strategy: ignore, no door you can afford will be able to stop a state-level actor.
I concur the question, "Who would have an incentive to spend resources on DDoS'ing Codeberg?" is a bit convoluted in mixing incentive and resources. But it's still, exactly, threat analysis, just not very useful threat analysis.
That's not how threat analysis works. That's a conspiracy theory. You need to consider the difficulty of achieving it.
Otherwise I could start speculating which large NAS provider is trying to DDoS me, when in fact it's a script kiddie.
As for who would have the most incentives? Unscrupulous AI scrapers. Every unprotected site experiences a flood of AI scrapers/bots.