What does the recent sharp increase in FED’s assets mean? Where is it coming from?

Since end of march, FED increased it assets quite sharply, and it looks against their recent restrictive monetary policy (higher policy rates, quantitative tightening) tightening plan: https://www.federalreserve.gov/monetarypolicy/bst_recenttrends.htm

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In the graph linked, when you select “Select Assets of the Federal Reserve” to see exactly what constitutes their assets, we see that Securities held outright are not behind the sharp increase in their assets. So what type of assets are they increasing? And why markets doesn't seem to care?