I've only experienced de-motivation from managers, personally. At least for me, motivation comes from ownership, impact, autonomy, respect. You can cause me to lose motivation in a lot of ways, but you can't really cause me to gain motivation unless you've already de-motivated me somehow.

You can de-motivate me in a lot of ways, some examples:

- throwing me or a coworker under the bus for your mistakes

- crediting yourself for the work of someone else

- attempting to "motivate" me when I'm already motivated

- manufacturing a sense of urgency, this is especially bad if you try to sustain this state all indefinitely

- using AI or market conditions as a fear tactic to motivate the team

- visibly engaging in any kind of nepotism

Honestly this list could go on and on, but those are some that come to mind.

Also:

- not letting me have ownership of what I build and dictating features

- not giving me autonomy of how to solve a problem