en.wikipedia.org/wiki/Friedrich_Olbricht

Contemporary and reference sources distinguish between the Army and the Armed Forces as separate commands.

• The German History in Documents and Images text on the November 5, 1937 Hossbach conference lists those present as "Commander-in-Chief of the Army Werner von Fritsch" and separately "Reich Minister of War Werner von Blomberg." In the document itself, Fritsch is again identified as "Commander in Chief, Army."
• The U.S. Holocaust Memorial Museum’s overview of the German Armed Forces High Command likewise states that Werner von Blomberg was "Commander in Chief of the Armed Forces until Hitler took over," while "Werner von Fritsch and Walther von Brauchitsch" were "Commanders in Chief of the Army."

So the article conflates two different offices: Fritsch led the Army (Heer), not the entire Armed Forces (Wehrmacht).

Official timelines from German military-history institutions separate early radio reports that Hitler had survived from Hitler’s own radio speech.

• The Bundeswehr’s chronology of July 20, 1944 states that after 17:00 radio reports were arranged saying Hitler had survived, but that "Gegen 01.00 Uhr Hitler spricht im Rundfunk" (“Around 1:00 a.m. Hitler speaks on the radio”). The same timeline says the conspirators were arrested and the coup had already been crushed before then: Fromm regained control at 23:00, the conspirators were executed at about 00:15, and only after that did Hitler speak on the radio.
• A separate Bundeswehr article on Hitler’s radio address explicitly says that by the time the broadcast vehicle reached the Wolfsschanze and Hitler spoke, "Zu dieser Zeit war der Umsturz in Berlin bereits gescheitert" (“By this time the coup in Berlin had already failed”).
• The German Resistance Memorial Center likewise says the conspirators realized late in the evening of July 20, 1944 that the coup had failed and were ordered shot shortly before midnight.

So the article incorrectly attributes the coup’s collapse to Hitler’s later radio speech. Earlier reports that he had survived contributed to confusion, but Hitler’s own speech came only after the coup was effectively over.

The article places Olbricht’s arrest at 21:00, but official timelines of the coup show he was still active well after that time.

• The Bundeswehr’s detailed chronology states that at 20:35 Olbricht was still giving orders: "Olbricht untersagt die Weitergabe des eingetroffenen Fernschreibens Keitels" (“Olbricht forbids the forwarding of Keitel’s telegram”).
• The same official chronology says that only around 23:00 did Fromm regain control of the Bendlerblock: "Fromm übernimmt wieder das Kommando im Bendlerblock. Er lässt die Verschwörer verhaften" (“Fromm takes command again in the Bendlerblock. He has the conspirators arrested”).
• The German Resistance Memorial Center likewise says the conspirators realized late in the evening that the coup had failed and were ordered shot shortly before midnight, which fits an arrest much later than 21:00.

So Olbricht was not arrested at 21:00; according to the official timelines, his arrest came only after Fromm retook command later that night.