Ehh, the dip buying is a bit more of a PR move in my opinion. He "only" bought 150 BTC, which is more or less $6.8 million. Whereas while El Salvador is definitely not a powerhouse country levels of wealthy, I don't think that $6.8 million will make a significant dent on their balance sheet.
This is the most likely explanation, the money that is being invested in bitcoin right now is not a huge deal for most countries, also as we know that money is going to be given away almost immediately so it's not a big deal if the price of bitcoin goes down a little bit after he buys it, so this is not a problem especially when we take into account that institutional investors have bought amounts of bitcoin way larger than that and they do not seem to want to sell their coins anytime soon.