It could be happens if Tron platform can attract great project to its platform, but as far as i know many of Developer prefer BSC to be the platform rather than tron.
It caused by BSC to have more hype compared with the tron. Remember that if BSC was also compliant with ethereum and that's the reason why people are still preferring to use BSC over tron. Basically, both were having the same cheap fees but it's not only about that. The hype around the blockchain ecosystem was also a very important thing.
Remember that NFT development will be much easier to be done on BSC compared with the tron which was using a different blockchain. So many exchange sites were also accepting the BSC asset transactions.
It can also be seen from how much the demand that already got by BSC project compared with the tron project. This is the reason why people were picking BSC over TRON.