Microsoft Research seems to have done some exciting things with provers over the years - Z3 is another significant program. All under the direction of Leonardo de Moura, notably.
Citation needed. I can make a perfectly reasonable Isar-style declarative proof in Lean. Just because most users of Lean choose not to do this doesn't mean it can't be done. I should mention that users are more willing to write imperative proof code instead of declarative in Lean is because 1) the interactive debugger is responsive and easy to use, and 2) writing a nicely structured declarative proof is more work than an imperative proof.