Galan007
|Quantum Observer|
The light novel implies that Broly wasn't trying to kill Freeza. Worth mentioning. /shrug
Regardless, I'd honestly chalk it up to Freeza becoming substantially more powerful since the ToP. After all, despite the massive gains he and Goku received during the ToP, as of this film Vegeta still believes that Freeza can "get even stronger and beat them", and specifically uses Freeza's gargantuan amp during RoF as a measuring stick. Heck, it's entirely possible that the events of the ToP alone bolstered Freeza's power significantly. I mean, the self-training he underwent for a few months during RoF was almost certainly not as rigorous as the fighting/beating he endured during the ToP.
On top of that, Freeza's always had arguably *the* best physical durability in the franchise(pound-for-pound), which likely helped him weather Broly's beatdown as well.