When two or more people are given responsibility does anyone really have it? When two or more people are put in charge of a task it’s too easy for a “he said/she said” scenario.
Instead, assign one person the responsibility (and give them the authority to get it done) and now you know who to hold accountable if something goes wrong (and who to credit when things go well).
When two or more people are responsible for something, ultimately no one is responsible. When one person is responsible, all doubt is removed.
Have a great day!