Even if Frieza had weakened a little bit after he was revived, than it still isnt weird how he got as strong as he did in DB super/Revival of F after training for several months.
When they fought him on namek, noone could handle him. Goku in base couldnt either.
Even as a super saiyan, he lost to a 100% full power frieza at first.
Frieza was this mighty, without training or hardly ever training.
Later after everyone got revived and summoned to earth (except Goku and Frieza), Goku won.
With frieza training for several months, it isnt really all that weird for him to reach to the power he did in db super/revival of F.
In db super/Revival of F, frieza in his final form (before golden), wasnt a match against Goku in his new base beyond god form.
Unlike on namek, where Goku needed super saiyan to win. That is a big change already and shows that Frieza in final form (before Golden) couldnt catch up to Goku in the relative short amount of time he had to train.
Frieza needed his gold form to be able to have a chance vs Goku SSJ blue.
We dont know how Frieza trained. We know very little about his race.
Frieza was already one of the strongest fighters in the uiverse in the frieza saga, without training or hardly ever training. He is a special case tbh. Apparently he has trouble finding reason to train. That is one of his weaknesses.
There are special rooms like the room of spirit in time.
Saiyans when near death and after battles, get huge power boosts.
Look at Goku when it happened multiple times in between his fight on earth vs vegeta, up until him becoming super saiyan vs Frieza. That is also a huge power increase from his earth fight in several ten thousands, to super saiyan lvl in the milions.
We dont know what special power increases and rooms the mutants among Frieza's race have.
We know that Frieza is special, having been as strong as he was in DBZ, while not training or hardly ever.
So it isnt weird for Frieza, among special cases, to have the big increase in power in DB super/revival of F.
As said, without his golden form he couldnt handle Goku without SSJ blue. Unlike on namek, where Goku needed to transform to stand a chance vs Frieza.
Frieza managing to find a new golden transformation, was what gave him a chance vs Goku SSJ blue.
In a sense, similar to how Goku needed to transform to SSJ to handle frieza final form in the past.