On bitcoin you could literally steal money with a good mempool attack, by closing a lightning channel with a previous state in your favor and censoring your peer to broadcast the real final state. There's good money to be made.

On Monero the only financial incentive is your government sponsored wage to de-anonymize users. It's motivating if got the job, but it's not like there's a sea of APT actors continuously looking on how to steal the cake, like North Korean Lazarus Group did on a bunch of ethereum L2 bridges (which I admit are much lower hanging fruits, but I'm sure one day they'll take a look into bitcoin L2s).