Price doesn’t stay under the last swing lows because there’s no supply from sellers to keep it down. The demand from buyers forces price action back up over the last swing low support. If there is no selling pressure at lower prices then demand will come in and the chart will rally.
Wyckoff Springs can occur in any market and on any time frame. Considering higher time frame charts can help increase the odds of success by looking at the multiple time frame trends. Market context is important to consider when using this signal as it has a higher probability of success when it occurs near other confluences of technical signals like oversold levels, key moving averages, or historical previous long term support on the chart.