The prophet delivers a sharp, tragic irony about the dangers of placing false confidence in military might over faith in God. Instead of relying on God, the people chose to depend on foreign alliances and imported Egyptian cavalry.
The people's intentions for these imported horses are understood in two ways. One approach suggests they wanted to be seen as elevated and proud, treating their majestic rides like raised banners [אבן עזרא, מצודת דוד, שד״ל, אברבנאל, ביאור שטיינזלץ]. This reflects a desire to adopt foreign culture and show off rather than trusting God, a vanity the prophet openly mocks [שד״ל]. Another perspective is more practical: the people planned to use these horses to escape quickly from their enemies, hoping to wait out the danger and eventually return home [רש״י, רד״ק, מלבי״ם].
In response, a punishment is promised that fits their actions perfectly. Those who hoped to be raised up proudly will instead suffer the humiliation of actual, desperate flight [מצודת דוד, אברבנאל, ביאור שטיינזלץ]. This grim reality unfolded when Sennacherib captured the cities of Judah, forcing the terrified population to flee from one city to another [שד״ל].
The people further boasted that they would ride on extremely fast horses or camels [אבן עזרא, רד״ק, ביאור שטיינזלץ], believing this speed would allow them either to chase down their enemies [מלבי״ם] or to escape to absolute safety [מצודת דוד]. This false confidence is countered with a harsh truth: the enemies chasing them will be even faster and stronger, easily catching up to them [רד״ק, מצודת דוד, אברבנאל]. This outcome is driven by a simple physical reality. A person fleeing for his life carries his belongings, weighing down his animal, while the pursuer rides light and unburdened, making his horse much faster [מלבי״ם].