If Parshuram was better than Arjuna, then why did he fail to defeat Bhishma

If Parshuram was better than Arjuna, then why did he fail to defeat Bhishma but the same Bhishma was defeated multiple times by Arjuna? there are two reasons why Parshurama was defeated by Bhishma first Parshurama had lost his Vishnu tej as per Valmiki Ramayana which had been transferred into Lord Rama. Parashu Rama opts for elimination of his ascetic merit and heavenly realms thereby. Rama releases the bow annihilating that merit and after that, Parashu Rama retreats into oblivion. That inflamed missile fired from the arms of Śrī Rāma agonized Parashurāma and returned back to Śrī Rām after snatching only the divine (Vaishanvi) spendour of Parashurāma.” In this amazing event the supreme lord Ram not only destroyed the ego of parashuram but also took back the Vishnu-tej present in his own ansh roop ParshurAma. Lord Vishnu blessed Parashuram with Supreme powers and also informed him that he will take back these powers when he comes in the form of Sri Rama - The Lord said, 'Oh Brahmin! Conclude (wind-up) your austerities; your efforts are successful. You shall be empowered with a fraction of me (i.e., by my potential powers). Slay Kartvirya who is the best in the clan of Haihaya but is the killer of his own father and for which purpose you have done such severe penances and austerties (Tapa). After doing that, kill all the Kshatriyas on this earth twenty one times repeatedly. After that, hand the earth over to sage Kashyap. Be blessed with peace and tranquility. I who am an indestructible and eternal supreme Soul—shall take birth (i.e., reveal or manifest myself as an incarnation) as ‘Ram’ in the household of Dasrath in TretaYug (the 2nd era of the 4 era celestial cycle of creation and destruction). At that time, you shall see me with my supreme power (i.e., my infinite cosmic energy in the form of Sita). At that moment, I shall take back from you those immense powers that I am bestowing upon you now. After that, till the end of the Kalpa, you would do austerities and penances and stay on this earth. Canto 7, Bala Kanda, Adhyatma Ramayana. note that Adhyatam Ramayana is as authentic as Valmiki Ramayana it was a story that happened in different kalpa and it was composed by Ved Vyasa as per Tulsidas Ramcharitmanas second reason why Parshurama was defeated by Bhishma that his strength had decreased from treta yug to dvapur yug, so he was very old and his reflex skills were slower as compared to Bhishma who was very young at that time. A prime Parshurama would have mopped the floor with Bhishma Hanuman's Words:— Time was different in krita yuga and it is different in treta and dvapara. This is the time of decay and I no longer possess that form. The earth, rivers, ranges, mountains, siddhas, gods and maharshis must all conform to time and adjust their forms from one yuga to another yuga. Strength, size and power decline, and then increase again. O extender of the Kuru lineage! Therefore, do not wish to see that form. I am conforming to the rules of the yugas and no one can overcome time. similarly Jabavant was million times powerful in Sata yuga as compared to treta yug. but in treta yug he was defeated by Kumbha and Mahaparshava. that does not mean they are powerful than him. Because Jabavant originally belonged to Sata yuga and during that time he had the capability to finish the entire army of Ravana alone. Same applies on Parshurama too. he simply did not belong to that yuga. Parshurama during Treta yug was extremely powerful. Even celestial sages like Vasishtha and others lost their consciousness just by the mere presence of Parashurama anger. While they were conversing, a wind began to rage. It made the earth tremble and brought down the auspicious trees. The sun was enveloped in darkness and none of the directions could be discerned. Everything was covered in ashes and the army was confounded. Vasishtha and the other sages and the king and his sons remained stationed there. Though all of them were in their senses, they seemed to be unconscious. As per Brahmanda purana Parshurama had destroyed the power of two Brahmastras using his ascetic energy and had saved the world from destruction. what could Praswapan astra of Bhishma do to Parshurama. And Brahmastra during Treta yug was so powerful that using it Indrajit killed 66 crore vanaras and Lakshmana using it would have wiped out the entire rakshasa race. Parashurama Killed One hundred Akshouhinis in just 1.36 Hours. WITH AN AXE. On seeing his heroic sons who were proficient in battle, Rāma took up his axe and fought with them in battle. Within a short period of only two Muhūrtas , Rāma hurriedly slew that army consisting of a hundred Akṣauhiṇīs. Parshurama fought a fierce battle with Ganesha on Mount Mahendra and broke his tusk using his parashu. and after that Ganesha was called as Ekdanta. Parshurama wrestled Mahadeva for 21 days and made a scar on his forehead using his parashu. hence he was called as Shiva parashu. What chance does Arjuna stand against him? He was defeated by Mahadeva in the form of a kirata who did not even use his full potential yet Arjuna was unable to cause a scratch to him. an out of prime Parshurama during dvapur yug would certainly lose to Arjuna. but Parshurama during his prime in Treta yug was superior to every warrior of Mahabharata except Krishna and Balarama. Bhishma and Arjuna were nowhere near a prime Parshurama in treta yug.