collapse under (something's) own weight

1. Literally, of a building, structure, item, etc., to be so heavy as to cause its own collapse. The giant skyscraper was so top-heavy that it ended up collapsing under its own weight. You need to add additional supports or else that scaffolding is going to collapse under its own weight. You can't stack all those heavy boxes on top of each other, or they'll collapse under their own weight!

2. By extension, to be or become so onerous, burdensome, or overbearing as to lead to its own downfall or ruin. The company acquired dozens of smaller businesses, but expanding into so many different markets proved to be too much for it to manage, and it ended up collapsing under its own weight. The empire spread itself thin trying to maintain control of so many different nations, and as unrest in those domains grew, it eventually collapsed under its own weight. The king's a fool. His systems of oppression will one day collapse under their own weight, as is so often the case.