The Rashba writes (שו”ת ח”א סתקפ”א):
מצוה לפרסם עושי מצוה
Unfortunately, nowadays, people’s decisions are largely affected by how the rich people behave. Just look at the power that Elon Musk and Bill Gates wield on matters like Covid and free speech. People respect their opinions.
When people see rich people give tzedaka, it inspires them to follow suit.
המעשה הוא העיקר – What will cause more people to give tzedaka? A plaque? Then make a plaque.
[This is similar to the idea of making a big deal out of Torah learning, with siyumim etc., because this shows that we value Torah. קנאת סופרים תרבה חכמה, people get inspired when we show the great value of learning. So it is with all mitzvos, including tzedaka]
מנחם שמו