Most "mad scientists" are actually just mad engineers
cowbirdsinlove.com
cowbirdsinlove.com
really, he needs to write better unit tests.
I am not sure if I like that.
In particular, fictional mad scientists tend to implicitly operate in the manner you describe: by the time they're building fully functional death rays with which to threaten the world, they've presumably carried out maybe tens or hundreds of experiments to see if the new form of radiation from a crystal meteorite energy source could be channelled and weaponized.
Mad engineers are dangerous. Mad scientists are harmless.
But yeah, it's a lot easier to make a "mad engineer" villain than a "mad scientist" villain. Mad scientists tend to be more suited to being secondary characters-- somebody so obsessed with discovery that their goal of scientific discovery conflicts with the protagonist.