You are correct. Instead of gaining seats in the Senate, the Republicans lost one. The Dems gained two Senate seats in 2021 when Trump's endorsed Senate candidates in Georgia lost. The Trump-endorsed Dr. Oz lost to Fetterman in PA, resulting in the Republicans losing a seat in the Senate, giving the Democrats the majority. Oz beat McCormick (the GOP favorite) by 0.1% in a field of 7. Another interesting fact is that Oz won the primary with only 31.2% of the vote. Almost 70% voted against Trump's choice.
“The Great Commonwealth of Pennsylvania has a tremendous opportunity to Save America by electing the brilliant and well-known Dr. Mehmet Oz for the United States Senate,” Trump said, in part. Later, at a rally in North Carolina, he said: “You know, when you’re in television for 18 years, that’s like a poll. That means people like you.”
Obviously, Trump was wrong. Fetterman beat Oz by 5%. I won't be surprised if I'm called a "hater" because I posted facts.