Avoid Newly Founded Startups at all cost

So there's this AI startup I interned at, founded in 2024. My internship was of 3 months initially, then they would decide for PPO. Claiming some HR issues, they extended the internship for another month. The stipend was very low. And it was a WFH internship. Then when they gave the PPO at the end, I rejected the offer, as it gave 50% variable pay, and had another offer from MNC, they called my behavior "unprofessional" and even didn't reply to my mails about relieving docs.