It might seem counter intuitive, though it may not be strength as much as predictability. Thry knew how to deal with Trump because the knew he would advocate for the country he lead. They don't really know what the Democrats are going to do. They can predict which moves would advance US interests, and then prepare to support or oppose those actions, but the the Dems do something that is totally detrimental to their own country. It's hard for foreign leaders to process that.