No evidence to back this up just pure educated and ignorant speculation given a general evaluation of the Coronavirus family.
We know of 7 human CoV. 4 circulate on a regular basis and are generally nothing-burgers. Europeans see them a lot.
Then we have MERS, which is a killing machine but can’t spread. We also have SARS-CoV1 (2003) who was just a bit better at getting around but not as good as MERS at killing.
And now we have SARS-CoV2 who learned to spread itself around in exchange for not being such a murder machine.